The use of environmental chloride and tritium to estimate total recharge to an unconfined aquifer
TL;DR: In this article, a portion of the Gambier plain underlain by an unconfined aquifer with readily definable hydrologic boundaries has been divided into a number of areas within which soil types have similar hydrological properties, and mean annual recharge has been estimated for each area using both the tritium concentration and the chloride concentration of water within the soil profile.
Abstract: A portion of the Gambier Plain underlain by an unconfined aquifer with readily definable hydrologic boundaries has been divided into a number of areas within which soil types have similar hydrologic properties. Mean annual recharge has been estimated for each area using both the tritium concentration and the chloride concentration of water within the soil profile. Good agreement was obtained between the two methods with local recharge varying between 50 and 250 mm year-1. Total mean annual recharge for the area has been estimated to be 2.4 ± 0.3 x 108 m3 year-1, and this compares favourably with an estimated discharge of 2.5 ± 0.3 x 108 m3 year-1.
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TL;DR: The reliability of recharge estimates using different tech- niques is variable as mentioned in this paper, and uncertainties in each approach to estimating recharge underscore the need for application of multiple techniques to increase the expected recharge rates at a site.
Abstract: DOI 10.1007/s10040-0010176-2 Abstract Various techniques are available to quantify recharge; however, choosing appropriate techniques is often difficult. Important considerations in choosing a technique include space/time scales, range, and reliabili- ty of recharge estimates based on different techniques; other factors may limit the application of particular tech- niques. The goal of the recharge study is important be- cause it may dictate the required space/time scales of the recharge estimates. Typical study goals include water-re- source evaluation, which requires information on re- charge over large spatial scales and on decadal time scales; and evaluation of aquifer vulnerability to contam- ination, which requires detailed information on spatial variability and preferential flow. The range of recharge rates that can be estimated using different approaches should be matched to expected recharge rates at a site. The reliability of recharge estimates using different tech- niques is variable. Techniques based on surface-water and unsaturated-zone data provide estimates of potential recharge, whereas those based on groundwater data gen- erally provide estimates of actual recharge. Uncertainties in each approach to estimating recharge underscore the need for application of multiple techniques to increase
1,562 citations
Cites background from "The use of environmental chloride a..."
...1007/s10040-0010176-2 Environmental tracers – chloride Environmental tracers such as chloride (Cl) are produced naturally in the Earth’s atmosphere and are used to estimate recharge rates (Allison and Hughes 1978; Scanlon 1991, 2000; Phillips 1994)....
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...…Journal (2002) 10:18–39 DOI 10.1007/s10040-0010176-2 Environmental tracers – chloride Environmental tracers such as chloride (Cl) are produced naturally in the Earth’s atmosphere and are used to estimate recharge rates (Allison and Hughes 1978; Scanlon 1991, 2000; Phillips 1994)....
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01 Sep 2010
TL;DR: In this article, a critical evaluation of the theory and assumptions that underlie methods for estimating rates of groundwater recharge is provided, with detailed explanations of the methods provided - allowing readers to apply many of the techniques themselves without needing to consult additional references.
Abstract: Understanding groundwater recharge is essential for successful management of water resources and modeling fluid and contaminant transport within the subsurface. This book provides a critical evaluation of the theory and assumptions that underlie methods for estimating rates of groundwater recharge. Detailed explanations of the methods are provided - allowing readers to apply many of the techniques themselves without needing to consult additional references. Numerous practical examples highlight benefits and limitations of each method. Approximately 900 references allow advanced practitioners to pursue additional information on any method. For the first time, theoretical and practical considerations for selecting and applying methods for estimating groundwater recharge are covered in a single volume with uniform presentation. Hydrogeologists, water-resource specialists, civil and agricultural engineers, Earth and environmental scientists and agronomists will benefit from this informative and practical book. It can serve as the primary text for a graduate-level course on groundwater recharge or as an adjunct text for courses on groundwater hydrology or hydrogeology. For the benefit of students and instructors, problem sets of varying difficulty are available at http://wwwbrr.cr.usgs.gov/projects/GW_Unsat/Recharge_Book/
570 citations
TL;DR: In a semi-arid area of southern Australia, a change in land use from Eucalyptus scrub to cropping with wheat is shown to have caused considerable change in the mechanism of the movement of soil water and the amount of deep drainage as discussed by the authors.
354 citations
TL;DR: In this paper, the authors applied solute and isotopic methods for evaluating recharge fluxes, runoff, and spatial and temporal distribution of recharge in the Southern High Plains aquifer of Texas and New Mexico.
Abstract: The High Plains aquifer underlying the semiarid Southern High Plains of Texas and New Mexico, USA was used to illustrate solute and isotopic methods for evaluating recharge fluxes, runoff, and spatial and temporal distribution of recharge. The chloride mass-balance method can provide, under certain conditions, a time-integrated technique for evaluation of recharge flux to regional aquifers that is independent of physical parameters. Applying this method to the High Plains aquifer of the Southern High Plains suggests that recharge flux is approximately 2% of precipitation, or approximately 11 ± 2 mm/y, consistent with previous estimates based on a variety of physically based measurements. The method is useful because long-term average precipitation and chloride concentrations in rain and ground water have less uncertainty and are generally less expensive to acquire than physically based parameters commonly used in analyzing recharge. Spatial and temporal distribution of recharge was evaluated by use of δ2H, δ18O, and tritium concentrations in both ground water and the unsaturated zone. Analyses suggest that nearly half of the recharge to the Southern High Plains occurs as piston flow through playa basin floors that occupy approximately 6% of the area, and that macropore recharge may be important in the remaining recharge. Tritium and chloride concentrations in the unsaturated zone were used in a new equation developed to quantify runoff. Using this equation and data from a representative basin, runoff was found to be 24 ± 3 mm/y; that is in close agreement with values obtained from water-balance measurements on experimental watersheds in the area. Such geochemical estimates are possible because tritium is used to calculate a recharge flux that is independent of precipitation and runoff, whereas recharge flux based on chloride concentration in the unsaturated zone is dependent upon the amount of runoff. The difference between these two estimates yields the amount of runoff to the basin.
323 citations
TL;DR: In this article, the authors used unsaturated zone chloride and matric suction profiles to estimate the response of the aquifer to the increased recharge of native vegetation in a semi-arid region of southern Australia.
282 citations
Cites background or methods from "The use of environmental chloride a..."
...Allison and Hughes (1983) showed that in a semi-arid...
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...Under steady state conditions, rates of recharge can be estimated from a chloride mass balance in the unsaturated zone (Allison and Hughes, 1978; Kitching et al., 1980; Peck et al., 1981; Edmunds et al., 1987)....
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...For example, Allison and Hughes (1978) successfully used this method for high rates of recharge (50-250 mm year-l)....
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...In most of the areas where development of secondary salinisation has been studied, the absolute increases in groundwater recharge have been greater than those reported by Allison and Hughes (1983), but the relative increases are often much less (e,g....
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References
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624 citations
TL;DR: In this article, a study of the possibility of using chloride concentrations in groundwater for estimating recharge rates is described, the application being demonstrated on available data from the Coastal Plain Aquifer in Israel.
242 citations
TL;DR: In this paper, the authors estimate that removal of forest vegetation from forested catchments has increased groundwater discharge of whole catchments by amounts ranging from about 1 to 13 cm3/cm2yr, and the characteristic times for equilibrium of chloride input and loss on farmed catchments are estimated to range from 30 to 400 years.
Abstract: Loss of chloride in streamflow (salt flow) from forested catchments in southwestern Australia is only slightly greater than the total annual input (salt fall) from rain and dust. However, salt flow from catchments in which a significant area of the forest vegetation has been cleared for farming is much larger and exceeds salt fall by up to 690 kg/ha yr, or a factor 21. The net loss of Cl is interpreted to result from decreased storage in catchment soil water. Removal of the forest vegetation is estimated to have increased groundwater discharge of whole catchments by amounts ranging from about 1 to 13 cm3/cm2yr. From present rates of groundwater discharge, characteristic times for equilibration of Cl input and loss on farmed catchments are estimated to range from 30 to 400 years. In equilibrium the salty streams draining farmed catchments would yield water with Cl concentrations acceptable for drinking.
159 citations
21 Mar 2013
154 citations