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Government of India & Government of The Netherlands DHV CONSULTANTS & DELFT HYDRAULICS with HALCROW, TAHAL, CES, ORG & JPS VOLUME 8 DATA PROCESSING AND ANALYSIS OPERATION MANUAL – PART IV GROUNDWATER RESOURCE ASSESSMENT

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page i Table of Contents 1 GROUNDWATER RESOURCE ASSESSMENTCONCEPT 1-1 1.1 RECHARGE COMPONENTS 1-1 1.2 DISCHARGE COMPONENTS 1-2 1.3 INDEPENDENT AND DEPENDENT COMPONENTS 1-3 1.4 STABILISING INFLUENCE OF THE DEPENDENT COMPONENTS 1-3 2 OBJECTIVES 2-1 2.1 ESTIMATION OF GROUNDWATER RESOURCE 2-1 2.2 VALIDATION 2-1 2.3 PRIORITISATION OF THE COMPONENTS 2-1 2.4 ESTIMATION OF AN UNKNOWN COMPONENT 2-2 3 CHOICE OF AREAL UNITS 3-1 3.1 MINIMISING THE DEPENDENT RECHARGE/ DISCHARGE COMPONENTS 3-1 3.2 IMMUNITY FROM EXTERNAL INFLUENCE 3-1 3.3 EVALUATION OF POSSIBLE AREAL UNITS 3-1 4 CHOICE OF WATER BALANCE PERIOD 4-1 5 COMPONENTS INCLUDED 5-1 6 ORGANIZATION OF THE DATABASE 6-1 6.1 DESCRIPTION OF THE AREA AND THE RETRIEVAL ZONES 6-1 6.2 DESCRIPTION OF THE AREAL BOUNDARY 6-1 6.3 DESCRIPTION OF THE PERIOD AND OBJECTIVE OF THE WATER BALANCE 6-1 6.4 RETRIEVAL OF DATA FROM THE BASIC MODULE 6-1 6.5 REVIEWING AND UPGRADING THE DATABASE 6-2 6.6 DIRECT ENTRY OF DATA 6-2 7 PROCESSING POINT DATA TO SPATIAL DISTRIBUTIONS 7-1 7.1 GENERATION OF CONTOURS/ SPATIAL DATA 7-1 7.2 WATER LEVEL DATA 7-1 7.3 AQUIFER PARAMETERS 7-1 7.4 RAINFALL 7-2 7.5 TOPOGRAPHICAL LEVEL 7-2 8 ESTIMATION OF WATER BALANCE COMPONENTS 8-1 8.1 STORAGE FLUCTUATION 8-1 8.2 RAINFALL RECHARGE 8-1 8.3 LATERAL FLOWS ACROSS BOUNDARY 8-2 8.4 STREAM AQUIFER INTER-FLOW 8-3 8.5 VERTICAL INTER-AQUIFER FLOW 8-3 8.6 EVAPOTRANSPIRATION FROM WATERTABLE 8-4 8.7 GW DRAFT 8-4 8.8 CANAL SEEPAGE 8-5 8.9 RECHARGE DUE TO RETURN FLOW FROM APPLIED IRRIGATION 8-5 8.10 RECHARGE FROM TANKS, PONDS, CHECK DAMS AND NALA BUNDS 8-5 9 TIME SERIES ANALYSIS 9-1 10 INTERFACING WITH THE GEC-97 NORMS 10-1 10.1 SALIENT FEATURES OF THE NORMS 10-1 10.2 IMPLEMENTATION OF THE NORMS 10-2 10.3 SUMMARY REPORT 10-4 11 REFERENCES 11-1

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 1-1 1 GROUNDWATER RESOURCE ASSESSMENT CONCEPT A groundwater (GW) balance study involves an application of the continuity equation to an aquifer (usually unconfined). The continuity equation in this context is a statement to the effect that the difference between the net recharge volume (I) and net discharge volume (O) equals the change of groundwater storage (∆S). I, O and ∆S must be in respect of the same aquifer area and the time period. I - O = ∆S (1.1) The continuity equation may be applied to a large area treating the entire study area as a single entity. The flow across the boundary is estimated by an application of Darcy’s law. Such a study is known as lumped water balance (LWB). Alternatively, the continuity equation may be applied at a micro level. Thus, the area of interest is divided into a finite number of cells and the continuity equation is applied to each cell. The flow between the adjacent cells is estimated by Darcy’s law. This approach could be termed as distributed water balance, and is conducted through the application of specialized software for groundwater modelling (such as the widely used MODFLOW). The dedicated software comprises a module on groundwater balance and GIS tools. The scope of the dedicated software is restricted to only the lumped water balance. Therefore, only the lumped water balance is addressed in the following text. The main advantage of the lumped water balance approach is its simplicity. The data processing comprises only simple arithmetic/graphical procedures devoid of any higher mathematics. In spite of its simplicity, this approach leads to validation of various procedures/ parameters. It also yields consistent estimates (that is, estimates satisfying the continuity equation) of various components of the recharge and discharge. These estimates in turn permit an estimation of the permissible groundwater development. The LWB permits only an analysis of current and historical data and as such is not a good tool for projection of the aquifer response. The area for a LWB study could be a basin (hydrologic and hydrogeologic), inter-basin or an administrative/ political unit. The time period could be a year, a season or a smaller unit like a fortnight or month and is only constrained by the frequency in which the basic data are monitored. The LWB study essentially comprises estimation of various components of the recharge/ discharge and the change of storage in a given area of the given aquifer in a given time period followed by an overall cross check for the consistency. 1.1 RECHARGE COMPONENTS The various components of the recharge are as follows. The components are classified as per the governing process. The governing processes are vertical flow through unsaturated and saturated zones; lateral (that is, predominantly horizontal flow) through the saturated zone; and vertical inter- aquifer flow (see Figure 1.1). Recharge as a consequence of vertical unsaturated flow • Rainfall recharge • Recharge from applied irrigation- either surface water or groundwater or both

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 1-2 Figure 1.1: Recharge as a consequence of vertical saturated flow • Recharge from canal seepage over the deep water table (depth below the canal bed more than 1.5 times the canal width at the free surface) • Recharge from storage tanks, ponds, percolation tanks, check dams and nala bunds over deep water table Recharge as a consequence of lateral saturated flow • Subsurface seepage from hydraulically connected drains • Subsurface horizontal inflow across a non-hydraulic boundary • Recharge from canal seepage to the shallow water table (depth below the canal bed less than 1.5 times the canal width at the free surface) • Recharge from storage tanks, ponds, percolation tanks, check dams and nala bunds over shallow water table Recharge as a consequence of vertical inter-aquifer flow • Recharge from an underlying leaky confined aquifer 1.2 DISCHARGE COMPONENTS The various components of the discharge are as follows. The components have been classified in accordance with the governing process. The governing processes are the vertical discharge through an external sink, saturated vertical and lateral flow, and inter-aquifer flow. Vertical discharge through an external sink • Groundwater pumpage • Evapotranspiration from shallow water table (within the capillary fringe/ root zone) Discharge as a consequence of lateral saturated flow • Subsurface outflow to hydraulically connected drains (rivers, sea) • Subsurface horizontal outflow across a non-hydraulic boundary Subsurface outflow to drains Groundwater draft Recharge from canal seepage Recharge from ponds or tanks Recharge from irrigation Rainfall recharge Evapotranspiration Leakage to underlying aquifer Subsurface groundwater outflow Subsurface groundwater inflow Recharge from underlying aquifer Change in groundwater storage: ∆S

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 1-3 Discharge as a consequence of vertical inter-aquifer flow • Leakage to an underlying leaky confined aquifer 1.3 INDEPENDENT AND DEPENDENT COMPONENTS Recharge and discharge as a consequence of the lateral saturated flow and the inter-aquifer flow and evapotranspiration are dependent upon the position of the water table. These are termed as the dependent components. Other components of recharge and discharge are almost independent of the position of the water table. These are termed as the independent components. This classification of the components has an important bearing upon the choice of an areal unit for groundwater resource assessment by LWB; and shall be referred back to subsequently. 1.4 STABILISING INFLUENCE OF THE DEPENDENT COMPONENTS A close examination of variation of the dependent components as a consequence of any temporal trend of water table, reveals that the variation tends to stabilise the causative trend. Thus, as the water table declines, the recharge components increase and the discharge components (including evapotranspiration) decrease. This tends to stabilise the falling trend. Similarly, as the water table rises, the recharge components decrease and the discharge components increase. This tends to stabilise the rising trend.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 2-1 2 OBJECTIVES Broadly speaking, a water balance study can serve one or more of the following objectives: 2.1 ESTIMATION OF GROUNDWATER RESOURCE The LWB as enumerated above provides the validated historical estimates of different components of recharge and discharge and as such may be used to estimate the status of the resource in a certain time span. Such estimation is an essential management tool for arriving at permissible groundwater draft and development stage. 2.2 VALIDATION Unfortunately many components of recharge and discharge can not always be estimated rationally either because of the complexity of the process or due to an inadequate database. These components are estimated empirically using some locally accepted (or some times even imported) norms/ practices. Even if rational algorithms are available and adopted, there would still be some uncertainty in the estimates on two counts. Firstly, even an apparently rational equation may have some hidden assumptions. Secondly, it would invariably comprise some parameters, which may not always be well known. Thus, there is some inherent uncertainty in the estimates of almost all the components of the water balance equation. This calls for a validation criterion. A water balance study can be taken up to validate various adopted algorithms (rational or empirical)/ norms/ practices/ parameter values. This can be accomplished by checking if the independently estimated components of recharge and discharge; and the storage change satisfy the water balance equation. For this purpose the water balance equation is rewritten as follows: I - O - ∆S = ε.∆S (2.1) Where: ε.∆S is the residue term in the water balance equation. This term can be viewed as the volumetric imbalance between the net recharge (that is, recharge minus discharge) and the storage fluctuation. The term ε is the normalized imbalance that is, the imbalance expressed as a fraction of the storage fluctuation. Ideally, the residue should be equal to zero. However, in practice it may at the best be a negligible quantity. Thus, a small enough residue may provide the desired validation. However, there is always a possibility that the errors in the estimates of the individual components may have compensated each other. Thus, the validation can never be absolute. Nevertheless, if the residues turn out to be small enough consistently over a number of time periods, one may be reasonably confident about the validation. Thus, it is necessary to carry out a multiple period water balance study. 2.3 PRIORITISATION OF THE COMPONENTS The above procedure apart from validating the various procedures/ parameters, also leads to an understanding of the relative significance of the various component(s) of the water balance. Estimate of each component is normalised by expressing it as a fraction of the storage fluctuation. These fractions are thus indices of the relative significance of the respective components. The indices can provide a basis for prioritisation of the components. Larger effort should be put in to estimate the high priority components and vice versa. Larger effort implies refining the algorithm and carrying out direct measurement of variables or conducting experimental field work to improve upon the estimates of the concerned parameters.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 2-2 2.4 ESTIMATION OF AN UNKNOWN COMPONENT It follows from the preceding discussion that many components of recharge occur as a consequence of flow through the unsaturated zone that extends from ground surface to the watertable. These components thus, need to be estimated by simulating the flow through the unsaturated zone. This simulation requires data on the soil and surface characteristics that are invariably not available on a regional scale. Further, the computational efforts may be prohibitively large. Thus, these recharge components are usually estimated empirically. This however, may introduce considerable uncertainty in the results of a water balance study. The uncertainty can be quite severe if a dominant/ crucial component is estimated empirically. This problem can be overcome by first identifying the most crucial component (say X) which is not amenable to a rational estimation. An example of X could be the rainfall recharge during a monsoon season. Subsequently, this component can be estimated by substituting the estimates of all other components and of the storage fluctuation into the water balance equation. The residual term (ε) is assumed to be zero. Thus, the estimate of X shall be reliable provided the estimates of all other components and of storage fluctuation are more or less error free. This calls for a precedent validation of the procedures/ parameters adopted for estimating components other than X. This is possible only if there exist seasons/ time periods during which these components are significant but the component X is insignificant or absent. If the estimates of these components during such seasons satisfy the water balance equation with consistently insignificant residue, the procedures/ parameters stand validated. Subsequently, these validated procedures/ parameters can be used to estimate the component X, as outlined above. Typically, this approach may be adopted for estimating the recharge from monsoon rainfall. The approach shall involve first dividing a hydrologic year into the monsoon and non-monsoon periods. The procedures/ parameters adopted for estimating components other than the monsoon recharge are first validated by carrying out multiple water balance of the non-monsoon seasons included in the database. Subsequently, the rainfall recharge is estimated by carrying out the water balance study of the monsoon seasons of the database. It is worthwhile to observe here that the average water tablefluctuation method of estimating the groundwater resource (R = ∆h.A.Sy) is essentially a simplified water balance of the monsoon period. In this method it is assumed that all discharge components (e.g., pumpage, evapotranspiration, etc.) and the recharge components other than the rainfall recharge (e.g., recharge from irrigation) are negligible as compared to the rainfall recharge.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 3-1 3 CHOICE OF AREAL UNITS The choice of an areal unit for assessment of groundwater resource by the LWB is governed by the following two considerations: 3.1 MINIMISING THE DEPENDENT RECHARGE/ DISCHARGE COMPONENTS Evapotranspiration, recharge and discharge as a consequence of the lateral saturated flow and the inter-aquifer flow are dependent upon the position of the water table. Thus, these components can not be assigned historical estimates while planning for future groundwater development/ recharge. These components (the dependent components) shall inevitably change as the planned groundwater development/ recharge takes place and the water table declines/ rises accordingly. Other components of recharge and discharge are almost independent of the position of the water table. Thus, the historical estimates of these components (the independent components), after due normalisation may hold for future planning. 3.2 IMMUNITY FROM EXTERNAL INFLUENCE For the sake of uniqueness, the areal unit may preferably be so selected that the groundwater resource is exclusively dependent upon the conditions there in and is independent of the pumping/recharge activity occurring outside the aquifer volume contained in the unit. 3.3 EVALUATION OF POSSIBLE AREAL UNITS A hydrogeological basin This is essentially an area bounded by impervious hydrogeological boundaries. Thus, the water table in the area is totally immune to the pumping/recharge activities occurring outside the area. It is also immune to the pumping activities (inside or outside the area) and boundary conditions in respect of the underlying confined aquifer. The resource of the unconfined aquifer in such a unit shall not depend upon what is happening out side (laterally as well as vertically). Thus, it shall not comprise any of the dependent components enumerated earlier (except for the evapotranspiration, which may not be activated unless the area is water logged). As such, this is an ideal unit for resource assessment by the LWB. However, such a unit shall no longer remain an ideal unit if the unconfined aquifer in the unit is underlain by a leaky confined aquifer. In such a case the unconfined aquifer is affected by the piezometric elevation of the underlying leaky confined aquifer and its position relative to the water tableelevation and hence by the pumping activities, and as such the resource can not be estimated uniquely by the LWB. However, if the vertical inter-aquifer flow is relatively small in magnitude, these effects may be negligible and as such, this may be a near ideal unit for resource assessment by the LWB. Hydrological (surface drainage) basin This is essentially an area bounded by a topographical divide. It is usually believed that a topographical divide is underlain be a water table divide but this may not always hold. Thus, the external influence and the dependent components could be significant. A hydrological unit thus, need not necessarily be an ideal unit for assessing the groundwater resource. As explained earlier in the context of a hydrogeological unit, the uncertainty is further aggravated in case the unconfined aquifer is hydraulically connected to an underlying leaky confined aquifer through an aquitard.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 3-2 In hard rock areas the topographical and hydrogeological divides may generally overlap each other. However, in alluvial areas and also in low relief hard rock terrain, an unconfined aquifer may cut across a topographical water divide and the lateral flows in alluvial aquifers may be relatively far more significant due to high transmissivities. Doab (Inter-basin) This is an area bounded by two major perennial streams fully penetrating the unconfined aquifer. Such stream boundaries ensure that there are no flows across the boundary. Thus, the water tablein the aquifer is immune to the pumping/ recharge activities out side the area. However, the component of the stream-aquifer inter-flow is prevalent and is dependent upon the position of the water tablerelative to the stream gauge. Further, even a doab would invariably have a non-hydraulic boundary across which the external influence may occur. Thus, it is also not an entirely appropriate unit for the estimation of resource by the LWB. An administrative unit In such a unit, all the dependent components of recharge and discharge are activated. The lateral inflows/outflows across the boundary are dependent upon pumping/ recharge events outside the areal unit. As such, an administrative unit is the least desirable but most commonly used areal unit. The only advantage of such a unit (which should not be underestimated) is that it falls under a single administration, which may enforce uniform data acquisition and management, practices.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 4-1 4 CHOICE OF WATER BALANCE PERIOD Theoretically speaking, a water balance study could be carried out for any period. However, in practice there are certain constraints, which are essentially derived from the intended objectives of the water balance study. For an optimal validation of the norms/ parameters etc., the period must permit the maximum possible activation of the concerned variables, and the components must be amenable to a reliable estimation. For example, if the objective is to estimate the specific yield by analysing the depletion of the water table/ storage during the dry season (as recommended in the GEC-97 norms), the period may incorporate the maximum possible decline from the view point of activation of the specific yield. This implies that the period may span between the discrete times of the highest and the lowest water table. However, a split to monthly water balance may be considered to minimise the error in the draft estimate (draft may be negligible in the first month after the monsoon season). For estimation of a specific component of the water balance, it is necessary to select a period during which the component is just fully generated. Any period less than that shall lead to an underestimation of the component. A longer period shall attenuate the predominance of the component and hence shall lead to a less reliable estimate of the component. For example, if the water balance is carried out for estimating the rainfall recharge by analysing the build up of the water table/storage during the monsoon season (as recommended in the GEC-97 norms), it shall be required to define a period during which the entire rainfall recharge just occurs. This period shall be necessarily different from the period of the monsoon rainfall because of the inevitable time lag. The period must span between the discrete times of the lowest and the highest water table and not the start and end of the rainy season. The frequency of manual monitoring of GW levels (usually two to four times a year under Indian practice) is generally not sufficient to define the seasonal hydrograph and therefore may miss either peak or low or both. The wide scale deployment of automatic water level recorders (DWLRs) implemented through the Hydrology Project, shall provide comprehensive and almost continuous water table hydrographs. These hydrographs shall permit a correct identification of the optimal period.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 5-1 5 COMPONENTS INCLUDED The dedicated software package includes modules and tools that permits a comprehensive water balance computation, which can be applied for estimation of groundwater resource in general, and in accordance with the GEC-97 norms in particular. The components of the water balance included in the module are (see also Figure 5.2): ∆S - the change of groundwater storage Rrf - recharge from rainfall Rc - seepage from canals Ri - recharge from irrigation Rt - recharge from storage tanks and ponds Rwc - recharge from conservation structures I - algebraic sum of lateral outflow (+) and inflow (-) across the boundary Dg - gross draft B- algebraic sum of subsurface outflow to (+) and inflow from (-) hydraulically connected streams L - algebraic sum of vertical inter-aquifer outflow (+) and inflow (-) E - outflow from the aquifer due to evapotranspiration from the aquifer The volumetric estimates of these components are substituted in the following equation: (Rrf + Rc + Ri + Rt + Rwc) - (I + Dg + B + L + E) - ∆S = ε.∆S (5.1) and ε is estimated. Figure 5.2: Components of the water balance Ri Rrf Rc Rt E L B Dg I ∆S Rwc

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 6-1 6 ORGANIZATION OF THE DATABASE The database necessary for estimating the components included in the above equation is organised in the following steps. 6.1 DESCRIPTION OF THE AREA AND THE RETRIEVAL ZONES The assessor is prompted to input the digitised boundary of the water balance area (termed henceforth as the unit area) and four reference circumscribing rectangles for the search of the observation wells, rain gauge stations, river gauging points and the pumping test points. The reference rectangles, oriented along the N-S and E-W directions, are defined in terms of the longitudes and latitudes of the sides. It may be appreciated that the data not only from the unit area, but also from beyond the boundary of the unit area could be relevant and useful for the study. The water level from an area extending up to the hydraulic boundaries (that is, a dyke or a hydraulically connected river or a GW divide) should be retrieved. The aquifer parameter data from area of similar hydrogeology should be retrieved. The rainfall data from meteorologically similar area should be retrieved. The river stage data from the upstream and down stream reaches having similar slope should be retrieved. This extension of the search areas shall permit more reliable spatial distributions, such as contouring, zoning, Thiessen`s polygons, interpolation, extrapolation; and identifying/ reconfirming hydrological/ hydrogeological boundaries. 6.2 DESCRIPTION OF THE AREAL BOUNDARY The assessor is then prompted to input the hydraulic description of the digitised boundary or its parts which could be a hydraulically connected river boundary, an impervious boundary or a GW divide, or a non-hydraulic (that is, administrative) boundary. Further, the assessor is prompted to extend the river alignment up to the corresponding reference rectangle. 6.3 DESCRIPTION OF THE PERIOD AND OBJECTIVE OF THE WATER BALANCE The assessor is then prompted to input the period of the water balance and the objective of the study (as already stated, the objective could be either validation or estimation). In case the objective is estimation, the assessor is prompted to indicate the component to be estimated. 6.4 RETRIEVAL OF DATA FROM THE BASIC MODULE Based upon the response of the assessor, the module retrieves the necessary basic data from the Basic module. The data comprise the following: • Coordinates and ground levels (above MSL) of the observation wells falling within and on the relevant reference rectangle, and the corresponding available water levels at all the discrete times falling in the period of the LWB. The water levels at the beginning and at the end of the period are mandatory. The water levels shall comprise water table elevations; and also piezometric elevations in case the vertical inter-aquifer flow is to be accounted for. Pre and post monsoon water table elevations of the preceding ten years are also retrieved for the trend analysis stipulated in the GEC-97 norms. However, if the database of the Basic module is not exhaustive enough to permit such retrieval, these data may be entered externally. • Coordinates of the rain gauge points falling within the relevant reference rectangle and the corresponding recorded rainfall depths within the stipulated period. However, if the database of

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 6-2 the Basic module is not exhaustive enough to permit such retrieval, these data may be entered externally. • Processed thematic maps (topographical contours, forest cover, hydrogeological and geomorphic units) in respect of the unit area. The forest cover may be defined in terms of boundary of well-defined forest area. In case there are no well-defined forests in the unit area, the average forest/ canopy cover expressed as a fraction of the geographical area may be entered. • In case a part (or whole) of the unit boundary comprises a river, the coordinates of the gauge stations (if any) falling within or on the relevant reference rectangle and the associated stage values at discrete times falling within the stipulated period. However, if the database of the Basic module is not exhaustive enough to permit such a retrieval, interpolated/ extrapolated river stage at a few points within the unit area along with the coordinates of the points may be entered externally. • Coordinates of the pumping test points falling within and on the relevant reference rectangle and the corresponding estimates of the relevant parameters. The relevant parameters are transmissivity and specific yield and also the hydraulic resistance of the aquitard in case the vertical inter-aquifer flow is to be accounted for. However, if the database of the Basic module is not exhaustive enough to permit such a retrieval, these data may be entered externally. • Blocks falling within the unit area, total area and the effective area (that is, area falling in the unit area) of each block, type wise number of groundwater production structures falling within the effective area of each block. However, if the database of the Basic module is not exhaustive enough to permit such a retrieval, these data may be entered externally 6.5 REVIEWING AND UPGRADING THE DATABASE The retrieved/ entered database in respect of water table, piezometric head, rainfall, pumping tests and river gauge are displayed. The database comprises the locations and the corresponding data magnitudes. These data locations symbolised appropriately shall be displayed superposed over the unit area and the reference rectangles. The data magnitudes shall be displayed at the respective locations. The assessor may view the database. There upon using his professional judgement he may exercise one of the following options: • Accept the database as such without any modification. • Delete any number of the retrieved data points (apparently inconsistent data, water level data from beyond a dyke or a hydraulically connected river, aquifer parameter data from a different hydrogeological zone, etc.). The data corresponding to the deleted points shall not be used for the subsequent calculations. • Redefine the domain(s) of any one or more of the reference rectangles to enhance the database. Thus, the assessor can iteratively modify his database till he is satisfied. 6.6 DIRECT ENTRY OF DATA The assessor shall be prompted to enter the following data directly: • Population density and fractional load on groundwater for domestic and industrial water supply, in the unit area (refer page 57 of the GEC-97 norms). • Wetted areas, bed reduced levels and running days in respect of the lined and unlined canals falling in the unit area. • The volumes of the canal water (released at the outlet) in the unit area during the stipulated time period for paddy and non-paddy crops.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 6-3 • The assessor will be prompted to state whether the stream is fully penetrating. If the answer is Yes, the attenuation factor shall be taken as 1.0. If the answer is No, the assessor is prompted to either enter the values of Wp, d and e (necessary for estimating the attenuation factor) or to directly enter the value (less than one) of the attenuation factor as per his hydrogeological judgement. • The assessor shall be prompted to enter the capillary height and evaporation rate for estimating the direct evaporation loss from the shallow water table areas. • The assessor shall be prompted to enter the root zone depth of the trees and the evapotranspiration rate for estimating the evapotranspiration from the forested areas.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 7-1 7 PROCESSING POINT DATA TO SPATIAL DISTRIBUTIONS The database so created shall be processed on a GIS platform in the following steps: 7.1 GENERATION OF CONTOURS/ SPATIAL DATA The module permits generation of contours and the corresponding spatial data in Raster/ Vector modes. As discussed subsequently, the assessor may use this capability for processing discrete point data of water level, aquifer parameters and rainfall. The processing involves the following steps: • The available discrete point data are analyzed by an appropriate algorithm (such as Kriging, Least squares polynomial, Spline function) and a Raster data set is generated. The pixel spacings of the Raster data shall be chosen by the assessor. • The assessor shall specify the desired contour interval. The Raster data are processed to generate and store Vector data corresponding to the resultant contours. • The assessor, using his professional judgement and guided by relevant maps etc. may edit some or all the contours manually. • Vector data and hence the Raster data corresponding to the edited contours are generated and stored together with the data corresponding to the unedited contours (if any). 7.2 WATER LEVEL DATA The retrieved water level and the river stage data are used for contouring. While drawing the water table contours, the interpolated/ extrapolated stage values along the boundary, are treated as the water table data. This ensures a compatibility along the boundary. The assessor is prompted to exercise his choice of the contouring algorithm. The module returns the contours of the water table and also of the piezometric head (if relevant) at all the discrete times. It also returns the contours of water table fluctuation (that is, water table elevation at the end of the period minus the water table elevation at the beginning of the season, or water table depth at the beginning of the season minus the water table depth at the end of the season). The assessor may edit the contours any number of times. Raster data corresponding to the finally accepted contours are stored (refer Section 6.7.1). 7.3 AQUIFER PARAMETERS The assessor has the following two options for obtaining the spatial distributions of transmissivity, specific yield, and also the hydraulic resistance, if relevant. • The assessor may decide to use the contouring capability of the dedicated software. There upon, he is prompted to exercise his choice of the contouring algorithm. The module returns the contours of the aquifer parameter. The assessor may edit the contours any number of times. Raster data corresponding to the finally accepted contours are stored (refer Section 6.7.1). • Usually the data are available at a very few points only and as such, automatic contouring (that is, the first choice) may not be applicable. The assessor may ask for a display of the unit area and thematic maps, with the concerned database superposed over it. He may define homogenous zones and define a value for each zone. In the absence of any hydrogeological support of such zones, the assessor may choose to define Thiessen’s polygons around the data points (see the following Section on Rainfall). Corresponding Raster data are generated and stored.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 7-2 For obtaining the spatial distribution of the infiltration factor usually only the second option shall be relevant. 7.4 RAINFALL The assessor has the following two options for estimating spatial distribution of rainfall over the unit area during the stipulated period. The estimation has to be essentially based upon the retrieved data of point rainfall depths, corrected for orographic effects. • The assessor may decide to use the contouring capability of the dedicated software. There upon, he is prompted to exercise his choice of the contouring algorithm. The recommended algorithm is Kriging. The module returns the contours (also known as isohyets) of the rainfall depth, with topographical contours superposed over them. The assessor may edit the contours any number of times. Raster data corresponding to the finally accepted contours are stored (refer Section 6.7.1). • The assessor may opt to estimate the average rainfall by Thiessen’s polygon approach. A Thiessen’s polygon is drawn for each rain gauge by joining the right bisectors of the straight lines joining the neighboring rain gauge points. Thus, all the points falling within any polygon are closer to the respective rain gauge station than to any other rain gauge point. Therefore, the rainfall within a Thiessen`s polygon is assumed to be equal to the rainfall recorded at the respective rain gauge. Corresponding spatial data are generated and stored. 7.5 TOPOGRAPHICAL LEVEL In case a processed topographical map is not available in the database, the topographical contours shall be obtained on the basis of the ground level data if available for the sites of the observation wells/ piezometers. The assessor is prompted to exercise his choice of the contouring algorithm. The module returns the contours of the topographical level. Corresponding Raster data are generated and stored.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 8-1 8 ESTIMATION OF WATER BALANCE COMPONENTS Subsequent to the contouring and spatial distribution, the components of the water balance enumerated above are estimated as follows: 8.1 STORAGE FLUCTUATION Using the Raster data of the water tablelevations at the period’s beginning (hb) and at the end (he) and of the specific yield, the storage fluctuation shall be estimated by a GIS assisted integration of the product of the spatially distributed water table fluctuation and the spatially distributed specific yield over the unit area (A). The integration is as follows: dASy)hbhe(S A ∫ −=∆ (8.1) The integration involves pixel by pixel calculation of the storage fluctuation (pixel area multiplied by pixel water tableelevation multiplied pixel specific yield) and summation. However if a uniform specific yield is assigned over the entire unit area or the area is divided into a few homogenous parts, the storage fluctuation is estimated as follows: ∑ ∫ −=∆ i Ai dAi)hbhe(SyiS (8.2) Where, Ai is the ith homogenous part having an average specific yield Syi. The assessor has an option of performing the calculations in a semi-automatic mode, if he so desires. In case this option is exercised, the storage fluctuation shall be computed in the following steps: • Draw contours of water table fluctuation (as described in 6.7.1). • Draw zones of equal specific yield (as described in 6.7.3). • Superpose the zones of the specific yield over the fluctuation contours. • Delineate the areas lying in between each pair of successive contours and the areal boundary. Divide each inter-contour area among the intersecting zones and measure the sub areas, so obtained. All the sub-areas of an inter-contour area are assigned an average water tablefluctuation equal to the arithmetic mean of the ratings of the enveloping contours. Estimate the storage change in each sub-area by multiplying the sub-area by its respective specific yield and the average water tablefluctuation. Estimate the total storage fluctuation by adding the estimated storage fluctuations in the sub-areas. 8.2 RAINFALL RECHARGE Using the Raster data of the rainfall (r) and the infiltration factor (α), the volume of rainfall recharge (R) shall be estimated by GIS assisted computation of the following integration over the unit area (A): ∫ α= A dArR (8.1) The assessor has an option of performing the calculations in a semi-automatic mode, if he so desires. In case this option is exercised, the rainfall recharge shall be computed in the following steps:

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 8-2 • Draw contours/ Thiessen’s polygons of rainfall depth (as described in 6.7.4). • Draw zones of assumed equal infiltration factor (as described in 6.7.3). • Superpose the zones over the rainfall contours/ Thiessen’s polygons. • In case rainfall contours have been drawn, delineate the areas lying in between each pair of successive contours and the areal boundary. Divide each inter-contour area among the intersecting zones and measure the sub areas, so obtained. All the subareas of an inter-contour area are assigned an average rainfall equal to the arithmetic mean of the ratings of the enveloping contours. Estimate the rainfall recharge in each subarea by multiplying the subarea by it’s respective infiltration factor and the rainfall depth. Estimate the total rainfall recharge by adding the estimated rainfall recharge in the subareas. • In case Thiessen’s polygons have been drawn, estimate the average infiltration factor over each polygon. Estimate the rainfall recharge by computing the recharge over each polygon by multiplying the corresponding recorded rainfall depth and the polygon’s area with the averaged infiltration factor. 8.3 LATERAL FLOWS ACROSS BOUNDARY Using the following Raster data: • Water tableelevations at the period’s beginning and end, • Water tableelevations at other intermediate discrete times, • Transmissivity, and the Vector data of the non-hydraulic boundary, the volume (I) of subsurface lateral flows (inflows and outflows) across the boundary shall be estimated in accordance with Darcy’s law, by integrating the product of water table gradient normal to the boundary (i) and the transmissivity (T) over the boundary (C) and the period (t) of the LWB. Since the water balance equation, as written in Section 6.5, treats the outflow as positive, an outward falling gradient is treated as positive and vice versa. The integration has been programmed in the module. ∫ ∫= t C TidCdtI (8.4) The estimation thus, shall essentially involve estimation of spatial gradients from the spatial water table data and the boundary alignment, followed by numerical integration over the boundary and the water balance period. The assessor has an option of performing the calculations in a semi-automatic mode, if he so desires. In case this option is exercised, the lateral flow shall be computed in the following steps: • Obtain contours of water table(above MSL) at the beginning, end and at other intervening discrete times, as per the data availability. • Mark the boundary across which the flow is to be computed on each contour map. • Divide the boundary length among segments of nearly uniform transmissivity. • Estimate the average hydraulic gradient across each segment at each discrete time. Hence estimate the corresponding flow rates by multiplying the segment length with the corresponding transmissivity and the estimated average hydraulic gradient. • Estimate the flow rate across the boundary at each discrete time by adding algebraically the corresponding computed flow rates across the segments. • Estimate the flow volume in each time period (falling in between two successive discrete times) by multiplying the time duration with the average flow rate. The latter may be taken as the arithmetic mean of the flow rates at the starting and the ending discrete time. • Estimate the total flow volume by adding the individual period-wise flow volumes.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 8-3 8.4 STREAM AQUIFER INTER-FLOW This component can be computed in the same way as the subsurface lateral flow in case of fully penetrating streams. However, in case of the partially penetrating streams, the integral shall have to be multiplied by an attenuation factor (less than 1.0) to account for the attenuation of the stream- aquifer inter-flows due to the partial penetration. The factor (f) can be computed as follows: )ed)(e5.0Wp5( )eWp5.0(Wp5 f ++ + = (8.5) Where Wp is the wetted parameter of the stream (defined as the length of contact between water and the stream bed, normal to the flow direction), d is the water depth in the stream and e is the saturated thickness of the aquifer below the stream. 8.5 VERTICAL INTER-AQUIFER FLOW Using the following Raster data: • Water table elevation at the period’s beginning and end • Water table elevations at the intervening discrete times • Piezometric elevation at the period’s beginning and end • Piezometric elevation at the intervening discrete times • Hydraulic resistance (C) of the intervening aquitard the vertical inter-aquifer flow volume (L) across the unit area (A), in the water balance period (t) shall be estimated by performing the following GIS assisted integration: dtdAL t A C hH ∫ ∫= − (8.6) where H and h are respectively the space-time variant water table elevation and the piezometric head. The assessor has an option of performing the calculations in a semi-automatic mode, if he so desires. In case this option is exercised, the vertical inter-aquifer flow shall be computed in the following steps: • Estimate the spatially averaged water table(H) and piezometric elevation (h) at each discrete time. • Estimate the spatially averaged hydraulic resistance (C). • Estimate the rate of vertical inter-aquifer flow rate (Lr) at each discrete time, using the following equation: C hH Lr − = (8.7) • Estimate the flow volume in each time period (falling in between two successive discrete times) by multiplying the time duration with the average flow rate. The latter may be taken as the arithmetic mean of the flow rates at the starting and the ending discrete time. • Estimate the total flow volume by adding the individual period-wise flow volume.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 8-4 8.6 EVAPOTRANSPIRATION FROM WATERTABLE This component (ETV) has two parts, that is, direct evaporation and evapotranspiration. Loss of water due to direct evaporation occurs from such unforested area where the depth to the water table is less than the capillary height. This loss can be estimated by integrating the time varying loss rate (volume per unit time) over the period of the water balance. The loss rate at different discrete times is the product of the corresponding evaporating areas and the evaporation rates. Both, the evaporating area as well as the evaporation rate varies with time. The dedicated software permits an estimation of the evaporating area (A1) at various discrete times for a given capillary height. The capillary height may vary from few tens of centimeters (for sands) to about three meters (for clays). The evaporation rates (E) may be close enough to the potential evaporation rate which could be estimated from pan evaporation rate. Loss of water due to evapotranspiration occurs from such forested area where the depth to the water tableis less than the root zone depth. This loss can also be estimated by integrating the time varying loss rate (volume per unit time) over the period of the water balance. The loss rate at different discrete times is the product of the corresponding evapotranspiring areas and the evapotranspiration rates. Both, the evapotranspiring area as well as the evapotranspiration rate varies with time. The dedicated software permits an estimation of the evapotranspiring area (A2) at various discrete times for a given root zone depth. The root zone depth may be of the order of a few meters. Both the evapotranspiration rates (ET) and the root zone depth could be ascertained from the local forest authorities. Using the following Raster data: • Water table depth at the period’s beginning and end, • Water table depth at the intervening discrete times, • Forested area, the areas A1 and A2 at different discrete times can be estimated through GIS. The volume of evapotranspiration (ETV) can be computed by the following numerical integration over the period (t) of the water balance. The integration has been programmed in the module. ∫ += t dt)ET.2AE.1A(ETV (8.8) In case there are no well defined forests in the unit area, the evapotranspiration may be estimated from the average forest/ canopy fraction, β (that is, average forest/canopy area per unit geographical area) and the area (A3) with water tabledepth ranging from the capillary height to the root zone depth. The area A3 at different discrete times can be estimated from the Raster data of the water tabledepth. The volume of evapotranspiration can be calculating by the following numerical integration programmed in the module: ∫ +β+β−= t dt]ET)3A1A(E.1A)1[(ETV (8.9) 8.7 GW DRAFT Since direct draft figures are almost non-existent, this component is estimated from the retrieved data of the block areas, and the block-wise number of groundwater production structures of different types (dug wells, various tube wells).

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 8-5 The number of structures (of different types) in the unit area shall be tentatively estimated assuming a uniform distribution within each block. These numbers (block-wise and type wise) along with the basic data shall be displayed on the console and the assessor shall be prompted to modify the numbers if he so desires. The modification could be on the basis of the assessor’s knowledge of the spatial distribution of the structures with in each block. Upon a reconciliation of the numbers the assessor is prompted to enter the fractions of the total annual pumpage occurring in the stipulated time period. The groundwater draft shall be computed from these data and the average annual gross drafts incorporated in the GEC-97 norms (refer pages 61 and 62 of the norms). The computed figure shall be displayed on the console. The assessor shall be prompted to modify the figure, if he so desires (refer paragraph 3 on page 60 of the GEC-97 norms). 8.8 CANAL SEEPAGE This component is estimated using the retrieved canal data. The calculations shall be performed in accordance with the criteria stipulated in the GEC-97 norms (refer Section 5.9.3, page 54 of the norms). However, the assessor may like to cross check and validate the estimated value by studying the data (if available) of recorded discharge at the upstream and downstream of the study area. The difference between the two discharge values is obviously the upper limit of the seepage. The true seepage has to be less than that due evaporation and diversion of water. The assessor shall be prompted to enter a new value, if he so desires. 8.9 RECHARGE DUE TO RETURN FLOW FROM APPLIED IRRIGATION This component is estimated using the retrieved data of the canal irrigation and the Raster data of the topographical levels and of the water tableelevations at the beginning and at the end of the stipulated period. These data shall be used to estimate the spatially and temporally averaged depth to watertable. The calculations shall be performed in accordance with criteria stipulated in the GEC-97 norms (refer Section 5.9.4, pages 54-55 of the norms). 8.10 RECHARGE FROM TANKS, PONDS, CHECK DAMS AND NALA BUNDS These components shall be estimated using the data of average area spread (for storage tanks and ponds) and of the gross storage (for percolation tanks, check dams and nala bunds). The assessor shall be prompted to enter these data. The calculations shall be performed in accordance with the criteria stipulated in the GEC-97 norms (refer Sections 5.9.5 and 5.9.6 on page 55 of the norms). However, the assessor may like to cross check and validate the estimated value by carrying out a water balance of the reservoir, considering among others, the storage fluctuation and evaporation. The latter could be estimated from the pan evaporation data .

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 9-1 9 TIME SERIES ANALYSIS The water balance study provides estimates of the recharge and the discharge components of the continuity equation. An excess of the net recharge over the net discharge should be reflected as a rising trend in the time series of the water table; and vice versa. Thus, there must be a consistency among the water balance estimates and the trend in the time series. This requirement can be used for an indirect validation of the water balance estimates. As such, it is desirable to follow up the water balance study by a time series analysis of spatially averaged as well as point water table data from a few representative wells. The analysis shall require GIS assisted spatial averaging followed by a check for first and second order stationarity. In case stationarity is not inferred, a regression analysis shall be carried out to determine the nature of the trend, that is, rising or falling and it’s rate over the years.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 10-1 10 INTERFACING WITH THE GEC-97 NORMS Groundwater estimation committee (97) has stipulated detailed norms for estimating the groundwater resource of unconfined aquifers. The norms essentially lie within the broad frame work of the lumped water balance approach described in the preceding paragraphs. Thus, the resource evaluation module of the dedicated software can be used to implement the procedures incorporated in the norms. 10.1 SALIENT FEATURES OF THE NORMS The salient features are as follows: Areal and time units The recommended areal unit for the hard rock areas is a hydrological basin. It is suggested that in hard rock areas the hydrological and hydrogeological boundaries may overlap and as such the groundwater flow across the boundaries of a hydrological basin may be negligible. Recognizing that in alluvial areas an aquifer may cut across a topographical divide, the recommended unit for alluvial areas is an administrative block. The recommended periods for the water balance are the monsoon and dry seasons. The dry season water balance (recommended only for non-command areas) is aimed at estimating the specific yield. The monsoon season water balance is aimed at estimating the rainfall recharge. Normalization of the monsoon rainfall recharge The recharge occurring in a normal monsoon year is estimated by analysing the results of the monsoon season water balance for the current and the preceding years. The data of the monsoon rainfall and the corresponding computed rainfall recharge are subject to a regression analysis, assuming a linear relationship (with or without a constant) between the monsoon rainfall and the corresponding recharge. The computed coefficient and the constant permit estimation of the rainfall recharge corresponding to a pre computed value of the normal monsoon rainfall. Categorization of areas for GW development The GEC-97 norms suggest a categorization of the areas for groundwater development (that is, safe, semi critical, critical and over exploited) on the basis of the stage of the groundwater development. The stage is defined as the ratio of the existing groundwater draft to the net annual groundwater availability. The net annual groundwater availability has been defined as the estimated resource minus a certain allowance for the natural groundwater discharge. The latter has been defined as the existing natural groundwater discharge during monsoon season plus a permitted natural groundwater discharge during dry season. The suggested figure for the permitted discharge is five to ten percent of the estimated resource. However, keeping in view the inherent uncertainties in the estimates of the existing groundwater draft and the resource, the norms further suggest a confirmation of the categorization by looking at the long-term trend of the water level in the unit. It is stipulated that a composite plot of the pre and post monsoon water levels of at least ten preceding years should be presented along with the stage calculations.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 10-2 Components not included The component of subsurface lateral inflow/ outflow has not been included in the suggested approach. However, it has been pointed out that this component may not always be negligible especially in the case of alluvial areas where the transmissivities are relatively large and choice of the assessment unit is based upon administrative consideration. Further, it is suggested that the assessor may like to estimate this component and include in the water balance equation appropriately. Stream-aquifer inter-flow has been ignored in the LWB for the monsoon season. This component could be quite significant in high transmissivity areas. Evapotranspiration over water logged and forested areas have been ignored for both the seasons. This component could be quite significant during monsoon period when the water table may be quite shallow. The inter-aquifer flow has also not been included. 10.2 IMPLEMENTATION OF THE NORMS The water balance of the dry and monsoon seasons and the post water balance calculations, envisaged in the norms can be implemented through integrated use of the resource assessment module and the GIS tools of the dedicated software. As discussed in the preceding Section, the norms suggest exclusion of a few components of the water balance equation. These components have apparently been excluded to avoid the subjectivity inherent in their manual/ graphical estimation. On the other hand the dedicated software, on account of a computerised/GIS approach, permits an easy and objective estimation of these components. Therefore, it is suggested that these components be included while implementing the norms through the dedicated software. Steps of the implementation shall be as follows: Dry season water balance The estimates of the all the recharge and discharge components and of the storage fluctuation are substituted in the continuity equation. The imbalance, expressed as a fraction of the storage fluctuation (magnitude) is computed and conveyed to the assessor. In case the imbalance is small enough, the assigned specific yield distribution stands corroborated. In addition, the estimates of the recharge components also stand corroborated. However, since the draft estimate is prone to possibly large errors, the validation may not be beyond doubt. Monsoon season water balance The principal end product is the rainfall recharge. This is estimated by substituting the estimates of the recharge components (other than the rainfall recharge), all the discharge components and the storage change into the continuity equation. Normalization of the rainfall recharge The normalization of the recharge is aimed at estimating the monsoon rainfall recharge corresponding to the normal monsoon rainfall. Such a study can be taken up provided the estimates of monsoon rainfall recharge have been arrived at for the preceding years. The normalization is accomplished by carrying out a regression analysis on the historical data of monsoon rainfall and the corresponding estimated monsoon rainfall recharge. The analysis provides a functional relation between the monsoon rainfall and the corresponding recharge.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 10-3 The dedicated software permits a rigorous regression between the monsoon rainfall (r) and the computed monsoon recharge (R). The analysis apart from estimating the coefficients, is aimed at arriving at the optimal form of the functional relation between the monsoon rainfall and the monsoon rainfall recharge. For example, it can be checked whether the suggested constant in the functional relation is statistically significant or whether the assumed linearity holds (refer equations 8a and 8d on pages 42-43 of the norms). The performance of more elaborate nonlinear functional relations could be evaluated for possible adoption. Functional relations included in the dedicated software are as follows. The assessor may design his own functional relations as well. R = Ar - B (R=0 if r < B/A) (10.1) n )Br(AR −= (R=0 if r< B) (10.2) The goodness of the finally adopted functional relation is quantified by computing the statistics of the regression including model efficiency (or the correlation coefficient). The assessor is prompted to enter the normal monsoon rainfall. The normal monsoon rainfall is usually taken as the arithmetic mean of last fifty years’ data. There upon, the normal monsoon rainfall recharge is estimated in accordance with the regressed functional relation. Estimation of the total annual recharge/net annual GW availability The total annual resource is estimated by adding the normalized monsoon recharge and the dry season recharge. The dedicated software permits estimation of the net annual groundwater availability as per the GEC-97 norms (refer Section 6.10.1.3); and also permits the assessor to suggest his own figures for the permitted natural discharge during the monsoon and the non-monsoon periods. The prevalent natural discharge during the two seasons, as estimated by the LWB, are displayed on the console to assist the assessor in taking a decision in this regard. Estimation of the stage of GW development The stage of the groundwater development is estimated in accordance with the GEC-97 norms (refer equation 15 on page 57 of the norms). Time series analysis The time series analysis aims at identifying the trends (that is, rising or falling) in pre and post monsoon water table elevations. The Raster data of the pre and post monsoon water table(elevation above MSL or depth below the ground) of the preceding ten years are generated. These data are integrated over the unit area to estimate the spatial averages. The magnitude as well as the sign of the trend (if any) are identified by subjecting the time series of these average levels/ depths to a trend analysis. The inferred trends in the pre and post monsoon water levels are accompanied by computerised plots of the averaged water levels. The levels/depths from all or a few representative wells are also plotted.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 10-4 10.3 SUMMARY REPORT GEC-97 norms require a presentation of a summary of the entire resource evaluation exercise in a standard form given on pages 68 to 70 of the norms. The module permits a computerised presentation of such a summary.

Operation Manual – Data Processing and Analysis (GW) Volume 8 – Part IV Data Processing and Analysis March 2003 Page 11-1 11 REFERENCES Ministry of Water Resources, Govt. of India, Ground Water Resource Estimation Committee-1997. New Delhi, 1997.

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