The Estimation of Groundwater Recharge by Soil Water Balance in Semi-arid Regions PDF Download

Author: Victor Hugo Mendes Eilers
Publisher:
ISBN:
Category :
Languages : en
Pages : 356

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Author: I. Simmers
Publisher: Springer Science & Business Media
ISBN: 9401577803
Category : Science
Languages : en
Pages : 503

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Book Description
In view of the rapidly expanding urban, industrial and agri cultural water requirements in many areas and the normally associated critical unreliability of surface water supplies in arid and semi-arid zones, groundwater exploration and use is of fundamental importance for logical economic development. Two interrelated facets should be evident in all such groundwater projects : (a) definition of groundwater recharge mechanisms and characteristics for identified geological formations, in order to determine whether exploitation in the long-term involves 'mining' of an es sentially 'fossil' resource or withdrawal from a dynamic supply. A solution to this aspect is essential for development of a re source management policy: (b) determination of recharge variability in time and space to thus enable determination of total aquifer input and to quantify such practical aspects as 'minimum risk' waste disposal locations and artificial recharge potential via (e.g.) devegetation or engi neering works. However, current international developments relating to natural recharge indicate the following 'problems' ; no single comprehensive estimation technique can yet be iden tified from the spectrum of methods available; all are reported to give suspect results.

Author: Laura Dean Garcia
Publisher:
ISBN:
Category : Arid regions
Languages : en
Pages : 347

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Author: Ian Simmers
Publisher: Routledge
ISBN: 1351419579
Category : Technology & Engineering
Languages : en
Pages : 240

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Book Description
Groundwater use is of fundamental importance to meet the rapidly expanding urban, industrial and agricultural water requirements in (semi) arid areas. Quantifying the current rate of groundwater recharge and define its variability in space and time are thus prerequesites for efficient groundwater resource managment in these regions, where such resources are often the key to economic development. Attention focuses on recharge of phreatic aquifers, often the most readily-available and affordable source of water in (semi) arid regions. These aquifers are also the most susceptible to contamination, with the recharge rate determining their level of vulnerability. (Semi) arid zone recharge can be highly variable, the greater the aridity, the smaller and potentially more variable the natural flux. Its determination is an iterative process, involving progressive data collection and resource evaluation; there is also a need to use more than one technique to verify results. Direct, localised and indirect recharge mechanisms from a spectrum of known sources are addressed in the framework of recharge from precipitation, intermittant flow and permanent water bodies. The approach taken for each of these reflects the nature and current understanding of the processes involved. The volume also reviews current recharge estimation challenges, outlines recent developments and offers guidance for potential solutions.

Author:
Publisher:
ISBN:
Category : Arid regions
Languages : en
Pages : 124

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Author: Richard W. Healy
Publisher: Cambridge University Press
ISBN: 1139491393
Category : Science
Languages : en
Pages :

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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/

Author:
Publisher: Cuvillier Verlag
ISBN: 3736918852
Category : Science
Languages : en
Pages : 184

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Regolith aquifers in the weathered zone overlying Precambrian basement rocks serve as the main source of groundwater in a large part of the Volta River basin in West Africa. A prerequisite for sustainable groundwater resources management is the knowledge of recharge processes and the annual recharge rate. This research assesses the water balance, and in particular the groundwater recharge rate, for the Atankwidi catchment, a 275 km² sub-catchment of the White Volta in northern Ghana. Large uncertainties are typically inherent in any singular method to determine groundwater recharge. For this reason, an integrated approach is developed in this work which makes use of several field methods and combines results from these methods with water budget modeling. Field methods included in this approach are groundwater level observations, isotope analyses and a Chloride mass balance. The Atankwidi catchment falls within the semi-arid Sudan-Savanna climate zone. The climate is characterized by high temperatures and a single rainy season from May to October with an average annual rainfall of 990 mm. The hydrogeological system consists of three aquifers: The discontinuous, shallow aquifer, the regolith aquifer and the fracture aquifer. The principal aquifer is the regolith aquifer in the weathered mantle, which is usually targeted for drinking water supply. It forms a continuous aquifer with an average saturated thickness of 25 m and a hydraulic conductivity of 2.5E-6 to 2.5E-5 m/s. Recharge rates vary considerably between wet and dry years and between locations, with a range of 2 % to 13 % of annual rainfall. The long term recharge rate is determined by the Chloride mass balance to be approximately 6 % of average annual rainfall. The research emphasizes the importance of high rainfall intensities in creating groundwater recharge. Interannual comparison of water level fluctuations shows that a decrease in annual rainfall of 20 % causes a reduction of groundwater recharge of 30 % to 60 %. The impact of changing quantities of annual rainfall on groundwater recharge is overestimated by methods that do not account for infiltration by preferential flow. A long term average groundwater recharge of 60 mm/y compares to a total current groundwater abstraction of 4 mm/y in the study area, which is one of the areas with the highest groundwater use per km² in the Volta River basin. Recharge is therefore currently not a limiting factor for groundwater resources development. Water budget modeling using WaSIM-ETH calculates that 63 % of annual rainfall is lost to evapotranspiration in a wet year (2003), and 82 % in a dry year (2004). In the investigated mesoscale catchment 23 % and 11 % of annual rainfall end up as surface run-off in a wet year and a dry year, respectively. Approximately 40 % of surface run-off consists of interflow, while the main fraction is direct run-off. Base flow from groundwater is negligible. Groundwater flow in the regolith aquifer is modeled with Visual Modflow, assuming average hydraulic conductivities as determined by pumping test evaluation. The model calculatesthat only about 5 % of groundwater recharge leaves the basin as groundwater flow. This is evidence that the regolith aquifer does not contribute to a large extent to regional groundwater flow. Leakage to localized zones of high hydraulic conductivity of the fracture aquifer, which underlies the regolith aquifer, could act as a main sink of groundwater recharge. However, the exact location and hydraulic properties of fracture zones are largely unknown, so that the flux from the regolith aquifer to these fractures as well as the amount of flow through fractures is impossible to estimate at present. Pumping tests with observation wells to assess the specific yield, long-term pumping test at the basin outlet and a continuation of groundwater hydrograph recording at high temporal resolution could largely enhance the knowledge of hydraulic properties in the future. The groundwater model could then be improved and extended to gain certainty on the characteristics of groundwater flow.

Author:
Publisher:
ISBN:
Category : Agricultural engineering
Languages : en
Pages : 416

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Author: K.-P. Seiler
Publisher: Springer Science & Business Media
ISBN: 1402053053
Category : Science
Languages : en
Pages : 257

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To face the threats to the water supply and to maintain sustainable water management policies, detailed knowledge is needed on the surface-to-subsurface transformation link in the water cycle. Recharge flux is covered in this book as well as many other groundwater issues, including a comparison of the traditional and modern approaches to determine groundwater recharge. The authors also explain in detail the fate of groundwater recharge in the subsurface by hydraulic and geologic means, in order to stimulate adapted groundwater-management strategies.

Author:
Publisher: American Geophysical Union
ISBN:
Category : Groundwater recharge
Languages : en
Pages : 298

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