Estimation of rainfall inputs and direct recharge to the deep unsaturated zone of southern Niger using the chloride profile method
TL;DR: In this paper, an estimate of direct groundwater recharge below a region of natural woodland (tiger bush) has been made in south-west Niger using the solute profile technique, which has been collected from a 77 m deep well drug within the study area covered by HAPEX-Sahel (Hydrological and Atmospheric Pilot Experiment), an international large-scale energy, water and carbon balance experiment carried out during the summer of 1992.
About: This article is published in Journal of Hydrology.The article was published on 1997-02-01. It has received 67 citations till now. The article focuses on the topics: Groundwater recharge & Water content.
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TL;DR: In this article , the authors developed 11 descriptors of climatic, topographic, vegetation, soil and geologic properties using global datasets, to characterise groundwater recharge controls in Africa.
Abstract: Groundwater is critical in supporting current and future reliable water supply throughout Africa. Although continental maps of groundwater storage and recharge have been developed, we currently lack a clear understanding on how the controls on groundwater recharge vary across the entire continent. Reviewing the existing literature, we synthesize information on reported groundwater recharge controls in Africa. We find that 15 out of 22 of these controls can be characterised using global datasets. We develop 11 descriptors of climatic, topographic, vegetation, soil and geologic properties using global datasets, to characterise groundwater recharge controls in Africa. These descriptors cluster Africa into 15 Recharge Landscape Units for which we expect recharge controls to be similar. Over 80% of the continents land area is organized by just nine of these units. We also find that aggregating the Units by similarity into four broader Recharge Landscapes (Desert, Dryland, Wet tropical and Wet tropical forest) provides a suitable level of landscape organisation to explain differences in ground-based long-term mean annual recharge and recharge ratio (annual recharge / annual precipitation) estimates. Furthermore, wetter Recharge Landscapes are more efficient in converting rainfall to recharge than drier Recharge Landscapes as well as having higher annual recharge rates. In Dryland Recharge Landscapes, we found that annual recharge rates largely varied according to mean annual precipitation, whereas recharge ratio estimates increase with increasing monthly variability in P-PET. However, we were unable to explain why ground-based estimates of recharge signatures vary across other Recharge Landscapes, in which there are fewer ground-based recharge estimates, using global datasets alone. Even in dryland regions, there is still considerable unexplained variability in the estimates of annual recharge and recharge ratio, stressing the limitations of global datasets for investigating ground-based information.
2 citations
01 Dec 2002
TL;DR: In this article, the authors applied the minimum entropy deconvolution (MED) for the estimation of the sequential groundwater recharge rate to evaluate the effect of any change in the groundwater system following the change in natural or artificial components.
Abstract: This study applies the minimum entropy deconvolution (MED) for the estimation of the sequential groundwater recharge rate. Groundwater recharge rates have conventionally been estimated as an average value over some period of time, e.g. annual or seasonal recharge rates. Such estimates however, are not suitable for the analysis of the dynamic sequential behavior of the groundwater head fluctuation. If the sequential groundwater recharge rate is obtained, numerical groundwater models can be effectively applied to evaluate the effect of any change in the groundwater system following the change in natural or artificial components. This study successfully applies MED to estimate the sequential recharge rates. As recharge rates are obtained by relative values, a series of timed observations are necessary. The validity of the estimated sequences of relative recharge rates can be checked by cross-referencing. Cross-correlations between the applied recharge sequence and the estimated results are above 0.985 in all study cases. Through the numerical test, the suitability of MED in the estimation of the recharge sequence to groundwater is investigated.
2 citations
TL;DR: In this article, the contribution of the practice of supplemental irrigation (SI) via excavated rainwater harvesting basin (RWHB) for mitigating effect of rainfall variability on agricultural production and impact of these RWHB on the dynamics of the water table.
Abstract: This study was carried out in the Burkinabe Sahel aimed at studying contribution of the practice of supplemental irrigation (SI) via excavated rainwater harvesting basin (RWHB) for mitigating effect of rainfall variability on agricultural production and impact of these RWHB on the dynamics of the water table. This study was conducted during two growing seasons (2013 and 2014) and used a test plot cultivated in corn and fitted out with measuring instruments to analyze water transfer in the soil-plant-atmosphere system on the one hand and the atmosphere-RWHB-water table system on the other hand. Four treatments—one under rainfall regime (T0) and three under SI (T1, T2, and T3)—were used in the experimental design to assess the contribution of the RWHB in improving corn yield. These SI were applied during the mid-season of corn (flowering, pollination, and grain filling). Water flow beneath a partially waterproofed RWHB was assessed using HYDRUS- 2D/3D program. Results showed that water stored in the RWHB allowed applying up to three SI, and increased corn yield up to 24% and 26% respectively in 2013 and 2014. However, SI targeting flowering and grain filling were the best scenarios to mitigate effect of dry spell in rainfed agriculture. Water flow under RWHB during the simulation period showed that dynamic of the saturated front depended on the magnitude of the water depth in the RWHB and the hydrodynamic characteristics of the underlying layers. Deep drainage was observed around 25th day after sowing (DAS) in 2013 and 45th DAS in 2014 according to water profile. This caused the decrease of the infiltration rate in the RWHB that was associated with a significant rise of 4% of the water table level ten days later in 2014. Recharge rate was estimated at 0.5 mm·d-1 during the mid-season and the late season of corn.
1 citations
TL;DR: In this article , the authors reported on groundwater recharge evaluation conducted in the area around Kanye village in southeast Botswana, using the chloride mass balance (CMB) technique, which revealed that the groundwater recharge ranges from 4.8 to 26.6 mm/yr.
Abstract: This paper reports on groundwater recharge evaluation conducted in the area around Kanye village in southeast Botswana, using the chloride mass balance (CMB) technique. Thirty-seven (37) years of rainfall data were examined to define the seasonal distribution and the average rainfall in the study area. The rainfall pattern through the twelve months of each year was further analysed using rainfall coefficient techniques. Thirteen (13) groundwater samples from different well-fields were collected during the rainy and dry seasons, and analysed for chloride and bromide concentrations. Additionally, chloride concentrations of the rainfall during the wet and dry seasons were obtained from a previous groundwater recharge evaluation study conducted in the same region. Two rainy seasons and one dry season are recognised in the Kanye area. The average annual rainfall in Kanye is 466 mm. 57% of this occurs in the first rainy season (January to April); 37% occurs in the second rainy season (October to December), and 6% occurs in the dry season (May to September). The CMB method reveals that the groundwater recharge ranges from 4.8 to 26.6 mm/yr. The recharge in the first rainy season is estimated to be 5.70%, whereas the recharge in the second rainy season and the dry season are 4.09 and 1.03%, respectively, of the average rainfall. The results show that large amounts of water are lost from the area in different forms after the rains. Harvesting the water lost as surface runoff could enhance the groundwater recharge of the Kanye area. • In Kanye area seven rainy months and five dry months are recognised throughout the year. • The groundwater recharge estimation of Kanye area was conducted using chloride mass balance method. • Recharge in Kanye area ranges from 4.8 mm/yr to 26.6 mm/yr. • The recharge in the seven months of the rainy seasons is 10.7% of the rains in these seasons.
1 citations
01 Jan 2022
TL;DR: In this article , the subsurface water resources changes caused by surrounding climatic variabilities are discussed thoroughly, and the role of varying climatic conditions on geochemical characteristics and pollutant transport is discussed in depth.
Abstract: Subsurface water resources have dynamic interactions with ground surface and its prevailing environmental conditions. Climate variability affects subsurface water resources both directly by altering surface water flux and indirectly via changes in groundwater extraction patterns. Dynamic climatic conditions are responsible for both the quantitative and the qualitative aspects associated with subsurface water resources. An improved understanding of impacts of climatic variability on subsurface water resources system is required for effective management of vadose zone and underlying groundwater reservoirs. Thus the main aim of this chapter is to present the subsurface water resources changes caused by surrounding climatic variabilities. First, the soil–water–atmospheric interactions under changing climate conditions are discussed thoroughly. Quantitative assessment of subsurface water storages and its flow under climate change conditions are elaborated and exemplified next. Thereafter, the role of varying climatic conditions on geochemical characteristics and pollutant transport is discussed in depth. Different aspects of modeling and practical approaches to identify the governing geo-hydrological processes in subsurface under varying environmental conditions are also reviewed comprehensively. Finally, a practical management framework is suggested on the basis of technical and socioeconomic aspects for implementing the potential mitigation measures associated with subsurface water resources under changing climatic conditions.
1 citations
References
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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.
361 citations
01 Jan 1988
TL;DR: A review of some of the physical, chemical and isotopic techniques available for estimating groundwater recharge can be found in this article, where the authors propose a model for estimating ground water recharge in arid and semi-arid regions.
Abstract: Groundwater recharge concepts.- Groundwater recharge concepts.- An unexpected factor affecting recharge from ephemeral river flow in SWA/Namibia.- On the continuity of aquifer systems on the crystalline basement of Burkina Faso.- Groundwater recharge estimation (Part 1): physical/chemical methods.- A review of some of the physical, chemical and isotopic techniques available for estimating groundwater recharge.- Evaporation in arid and semi-arid regions.- Satellite remote sensing and energy balance modeling for water balance assessment in (semi-)arid regions.- A proposed study of recharge processes in fracture aquifers of semi-arid Botswana.- Estimation of natural groundwater recharge under Saudi Arabian arid climatic conditions.- Solute profile techniques for recharge estimation in semi-arid and arid terrain.- Recharge estimation from the depth-distribution of environmental chloride in the unsaturated zone - Western Australian examples.- Natural recharge measurements in the hard rock regions of semi-arid India using tritium injection - a review.- Comparison of recharge estimates from injected tritium technique and regional hydrological modelling in the case of a granitic basin in semi-arid India.- Studies on natural recharge to the groundwater by isotope techniques in arid Western Rajasthan, India.- Groundwater recharge estimation (Part 2): numerical modelling techniques.- Numerical and conceptual models for recharge estimation in arid and semi-arid zones.- Methods for estimation of natural groundwater recharge directly from precipitation - comparative studies in sandy till.- The principles of inverse modelling for estimation of recharge from hydraulic head.- Estimating natural recharge of ground water by moisture accounting and convolution.- Natural ground water recharge estimation methodologies in India.- BALSEQ - a model for the estimation of water balances, including aquifer recharges, requiring scarce hydrologic data.- Applications and case studies.- Quantification of groundwater recharge in arid regions: a practical view for resource development and management.- Groundwater recharge studies in semi-arid Botswana - a review.- Rainfall-runoff-recharge relationships in the basement rocks of Zimbabwe.- Recharge characteristics of aquifers of Jeddah-Makkah Taif region.- Groundwater recharge and subsurface flow in the Comodoro Rivadavia area, Chubut Province, Argentina. Isotopic and hydrochemical study.- Groundwater recharge over Western Saudi Arabia.- Natural recharge of karst aquifers in Western Taurus region (southwestern Turkey).- Estimation of recharge of sand aquifer of the Island of Mannar Sri Lanka.- Groundwater recharge from three cheap and independent methods in the small watersheds of the rainforest belt of Nigeria.- Quantitative estimation of ground-water recharge in dolomite.- Quantitative estimation of ground-water recharge in the Pretoria-Rietondale area.- Analysis of long-duration piezometric records from Burkina Faso used to determine aquifer recharge.- Humid zone recharge: a comparative analysis.- Humid and arid zone groundwater recharge - a comparative analysis.- List of participants.
200 citations
TL;DR: In this paper, a more general use of the filter-paper method for measuring soil-water potential over a very wide range of values is advocated, both for in situ and laboratory situations.
188 citations
TL;DR: In this article, the causes of crust formation and its effect on the infiltration rate are discussed on untilled soils, and the presence of a crust is a permanent feature on these soils.
Abstract: Sandy soils of the Sahel area in West Africa, mainly cropped to millet (Pennisetum typhoides) are very sensitive to crust formation Crusts strongly reduce infiltration capacity In this area most fields are gently sloping (1–3%) and hence runoff is a widespread phenomenon; on the average 25% of the rain (mainly in the form of a few large storms during the rainy season) is lost by runoff The causes of crust formation and its effect on the infiltration rate are discussed On untilled soils the presence of a crust is a permanent feature Rainfall characteristics play a key role in crust formation Major rainfall characteristics of the Sahel differ significantly from those of other semi-arid areas
166 citations
158 citations