How we can calculate or estimate the quantity of ground water available in a particular region?

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It is appreciated If anybody can help answer how to estimate the quantity of ground water in a particular region, or group of regions. Links and a description of methods to evaluate the ground water quantity in a particular region or regions much appreciated.

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11 Answers

  2. Volumetric advance estimation of the exact quantity of regional groundwater in a region is difficult, and no method is foolproof. Conventionally, studies on regional groundwater systems adopt the approach based on gravity induced flow from high to low hydraulic head. Conventional hydro-geologic characterization methods learn about the aquifer by looking at data from well pumping tests to learn about the porosity, permeability, and other properties of the aquifer. Drawback of conventional methods is that the natural heterogeneities in an aquifer are difficult to characterize without detailed geologic information. Additional data can be gathered only by drilling more wells. Drilling costs are particularly high in an arid region where the water table is sometimes very deep below the surface. Moreover, if the test site is cover several square kilometers, it could necessitate hundreds of drilling sites. However, sometimes in the absence of adequate hydraulic data, it is difficult to estimate key parameters by numerical simulations techniques. Moreover, the water table distribution analyses provide a short-term feature. Modeling can be useful to some extent to estimate GW quantity approximately in the pursuit of sustainable solutions, only if it addresses not only economic efficiency and technical merits, but also the preferences and priorities of stakeholders. The isotope tracers occupy a special place, in this context, since, tracers only can give a detailed direct insight into many of the long-term processes of the water movement and distribution within the hidden groundwater system, in integration with hydro-chemical information, GIS, etc. In India, isotope tracer techniques have been used extensively for over three decades, to study groundwater occurrence, "age", recharge mechanism, flow regime, pathways, stratification, hydrodynamic zones, contamination characteristics, groundwater-surface water interactions, and mixing processes in groundwater system; and has been proved to be quite helpful, through some of the internationally acclaimed case studies.

  3. I agree with John. Geology and recharge have been mapped with airborne geophysics. The SkyTEM system from Denmark mapped depth to and depth of an important aquifer in Nebraska. A cool interactive Google map showing the results can be found at http://www.lpsnrd.org/Programs/gwaem.htm. For a description of the technology KQED on the PBS network did a short video of the Nebraska project showing a 3D image of the mapped aquifer. Volumes of available water can be extracted from the data. The video is here http://video.pbs.org/video/2365289913/.

  4. Dear Indra, Your question is too broad to provide you a succinct answer. When looking at even small, single well removals, a pump test will only give you a "snapshot" view of the available water. To develop a local or regional watershed inventory of water availability you will need to know the (1) the geology of the region; (2) the available recharge rates (basically the entire hydrologic cycle for the region); (3) a reasonable distribution of wells that have documented pumping rates along with depth from surface to top of aquifer; and (4) the ability to perform pump tests to gauge recharge rates for that period (it would be best to conduct separate pump tests during each season.) If you would like to further discuss the concepts entailed contact me at jrackerman@twinoaks.biz.

  5. Dear Indra Vijitha, Computation of Ground-Water Volumes Some calculations are available for estimation of ground water, but not foolproof procedure.Some techniques are developed in USA for finding ground water estimations,e.g.-sonic water level estimation,some eqations and formulae given for estimation of ground water level. The computation of volume of water in storage is illustrated with a hypothetical schematic of the basin attached fig-1. This schematic shows three of the six hydrogeologic units as nested bowls, with the bowl in the center of the basin, labeled as Tongue River-Wasatch aquifer, as the uppermost unit. The hydro geologic units increase in age with depth and outward from the centre of the basin. This schematic shows the water table not intersecting the land surface; however, areas may exist in the basin where this may happen. At any location, the saturated thickness for the Tongue River-Wasatch aquifer is given by a, which is the distance between the water table and the base of the Tongue River-Wasatch aquifer. The saturated thickness for the next lowest units, part of the Fort Union Formation, is more complicated. In areas where the potentiometric surface of Tullock aquifer is above the base of the Tongue River-Wasatch aquifer, the Tullock aquifer is confined and the saturated thickness of the Tullock aquifer, b, also is the apparent thickness of the Tullock aquifer. With increasing distance from the center of the basin, an area is reached where the water table is below the contact between the Tongue River-Wasatch aquifer and the Lebo Confining Unit (B). In this area (B), the Tongue River-Wasatch aquifer is completely unsaturated or absent. The amount of saturated thickness, c, is the difference between the water table and the base of the Tullock aquifer. The transition of aquifers between confined and unconfined conditions is poorly understood. On figure 5, the Tullock aquifer is confined at b. Applied Hydrology and Greystone Environmental Consultants, Inc. (2002, Appendix B) report that aquifer test results in alluvial sediments, which are part of the Tongue River-Wasatch aquifer as described in this report, indicate that at some depth even these materials act in a confined manner. In this study, an assumption was made that when a hydrogeologic unit has more than 50 feet of saturated thickness, it is confined. Thus, specific yield was used as the storage factor for a saturated thickness of 50 feet or less, and specific storage was used as the storage factor for a saturated thickness greater than 50 feet. Water-table data were from Hotchkiss and Levings (1986). The water table in the center of the basin (A in fig. 5) is from the approximate potentiometric surface in the Tongue River-Wasatch aquifer, whereas the water table (B in fig. 5) in stratigraphically lower units, represented by the Tullock aquifer in figure 5, is from potentiometric surface maps of other hydrogeologic units used in this report and given in Hotchkiss and Levings (1986). In some areas of the study, potentiometric contours of Hotchkiss and Levings (1986) did not extend to the edge of the outcrop. In these areas, water levels in shallow wells were obtained from the USGS Ground-Water Site Inventory database and a point coverage was made of these water levels. A TIN was assembled from this coverage. This was done only in areas where contoured water levels of Hotchkiss and Levings (1986) were not available. Any perched water-table zones were ignored in the calculation of ground-water volumes. The assumption was made that the extent of perched zones is small when compared to the entire area of the basin. For all volume estimates of saturated rock using the first method to estimate ground-water volume, the total volume of water was calculated by summing a component of water in sands and a component of water in non-sands. For the unconfined part of the aquifers, equation 1 was used to calculate the total amount of water in the sands: sand water = 1,000 * 1,000 * (sattk * ( % sand/100) * sand-porosity) (1) where: sandwater = the total amount of water in the sands, in cubic feet, 1,000 * 1,000 = the area of the grid cell, in square feet, sattk = the saturated thickness figure-1, in feet, %sand = the percentage of sand, and sand-porosity = the porosity of the sand. Equation 2 was used to calculate the total amount of water in the non-sand part of the cell: nonsandwater = 1,000 * 1,000 * (sattk * ( ( 100 - %sand) / 100) * non-sand porosity) (2) where: nonsandwater = the total amount of water in the non-sand component of the cell, in cubic feet, 1,000 * 1,000 = the area of the grid cell, in square feet, sattk = the saturated thickness (a in figure 5), in feet, %sand = the percentage of sand, and non-sand porosity = the porosity of the non-sand component. sfhvs = 1,000 * 1,000 * (fhtk * (fhsnd / 100) * Ssnd) * (trwsattk) (3) where: sfhvs = the volume of water released from confined storage in the sand part of the Fox Hills-Lower Hell Creek aquifer, in cubic feet, 1,000 * 1,000 = the area of the grid cell, in square feet, fhtk = the confined thickness of the Fox Hills-Lower Hell Creek aquifer, in feet, fhsnd = the percentage of sand in the Fox Hills-Lower Hell Creek aquifer, Ssnd = specific storage for sand, in feet-1, and trwsattk = the saturated thickness in the Tongue River-Wasatch aquifer, in feet. The procedure using equation 3 for the Fox Hills-Lower Hell Creek aquifer was repeated for each hydrogeologic unit. Estimated ground-water volumes were determined for the sand and non-sand parts of each unit using appropriate values of confined thickness, percentage sand, and specific storage.

  6. It's not specifically question and there is no specific answer, however we can estimate the quality and quantity of ground water in certian aquifer by carry out hydraulic ground water modeling includes carry out pumping test for wells within the aquifer area as much as possible, one nessacry thing is aware about the geological formation, actually we shall determined three groundwater hydraulic parameters (storativity, storage yield, conducdivity, ..etc.). When get that main parameters we used it in groundwater modeling software

  7. No straightforward answer, as it's context specific. For example, if you're accessing groundwater with surface mounted centrifugal pumps, you're interested in shallow unconfined aquifers where the water-table is less than 10 m below the surface. I can share several recent papers, if you contact me at csteley@mac.com.

  8. By drilling at one point check the dynamic and static size of ground water table and then calculate the volume of water available in that particular tegion

  10. We are the mfg. of sonic water level meters for long term monitoring and recharge rates. We have many municipalities in the US that use our Well Watch units on monitoring wells and boreholes so they can estimate the amount of water in the region. I do not know what methods they use to evaluate it but I know they do it using our devices. http://www.enoscientific.com/well-watch-670.htm

  11. Dear, You can try create a model for this study area then check the zonal budget to estimate the amount of water recharge or discharge from the study area