An assessment of groundwater recharge estimation techniques for sustainable resource management

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.

Understanding groundwater recharge mechanisms is essential for reliable groundwater recharge estimation for sustainable groundwater resource assessment and management, especially in arid and semiarid areas. In this study, chloride, together with stable isotopes (18O and2H), in 1‐year rainfall, soil water from representative profiles, and groundwater samples, collected in the Ordos Plateau, northern China were analysed. Groundwater recharge was estimated using unsaturated‐ and saturated‐zone chloride mass balance (CMB). An equation that describes the relationship between chloride concentrations in saturated zone water (Csz) and soil water residence time (τ) was derived. With the help of the relationship, chloride concentrations in unsaturated zone water (Cuz) and in groundwater (Csz) can be used to uncover water flow and chloride transport in the unsaturated zone. The relationship betweenCszandCuzindicates that, the groundwater was recharged mainly by intense rainfall events. Small rainfall events did not lead to groundwater recharge but contributed to the flux of chloride to soil surface. Stable isotopic compositions of18O and2H provided corroborative evidence of the recharge processes. The relationship betweenCszandτindicates further that there is no source of chloride in the groundwater other than that from precipitation. Thus,Cszcan give more reliable recharge estimates.Cuzwas influenced by heavy rainfall‐induced runoff, run‐on and bypass flow events and cannot give reliable recharge estimates. However, if used jointly withCsz,Cuzcan help to gain insights into recharge processes and yield groundwater recharge estimates with higher certainty. The outcomes of this study can assist for groundwater recharge investigation and assessment in regions where the assumptions and boundary conditions necessary for the correct application of the CMB method may not be met.

Groundwater recharge study is essential because it provides information on the groundwater flow and availability, and its sustainable management over many years. Groundwater recharge estimation also helps evaluating the characteristics of aquifer, such as its bearing capacity and susceptibility to contamination. Many studies so far have focused on several techniques and methods of estimation of groundwater recharge. These methods were very simple, such as seepage meter or tracer techniques, and even complex numerical modelling. However, picking up the right techniques from multiple require essential considerations such as physiography and climatic condition of the location, reliability of the technique, cost and resource availability, and other unavoidable factors that may put limitations in the applicability of a particular method. Furthermore, the reliability of a recharge estimation method also depends on the recharge rates of a particular site. Therefore, an appropriate technique of recharge estimation should be taken such that the estimation resolution of that technique is matched with the average recharge rates of that site. This paper discusses various recharge methods to select a suitable approach appropriate for the climatic condition of Bangladesh. Estimating groundwater recharge by only one method may result in several errors and draw a wrong conclusion. Applying multiple approaches can minimize these errors and enhance the acceptability of the recharge estimates. Bangladesh Rice J. 25 (2) : 45-56, 2021

Groundwater recharge is the most important component in all the water balance studies and in ground water development projects as a part of sustainable groundwater management. Norms set by the Groundwater Resource Estimation Committee, GEC-2015 was used for the estimation of recharge. The study was conducted for the Bandar canal command area constituting the Krishna Central Delta in Andhra Pradesh. Following the norms of GEC-2015, the recharge was estimated for the past decade from 2012-13 to 2021-22 and it was found that recharge rate ranged from 438135.8 ha-m in the year 2015-16 to 1677730 ha-m in the year 2013-14. While computing the gross recharge, recharge attributed by rainfall, canal seepage, irrigation return flow and from the ponds/tanks are considered. Recharge estimated sheds information on replenishment and improved management of coastal aquifers where seawater intrusion is a major problem.

Since groundwater is an integral component of natural hydrologic systems, an estimation of groundwater recharge is required to understand the changes in the temporal water budget and groundwater flow system. The rate of groundwater recharge varies widely in space and time particularly in arid to semiarid regions, and it is rather difficult to measure recharge directly. The aim of this study was to assess the natural groundwater recharge in Al Zerba catchment and the interaction between the surface and groundwater. The catchment is classified as an arid to semiarid climate with an aridity index of 0.25 to 0.3 and long-term average annual precipitation ranging from 300 to 350 mm. Delineation of the catchment boundary was carried out using spatial interpolation of elevation data extracted from the digital elevation model. The effects of vegetation and abstraction from pumping wells on the groundwater table were investigated. Furthermore, groundwater recharge was estimated based on water budget, water table fluctuation analysis by using rainfall infiltration breakthrough, and soil water balance using hydrologic evaluation of landfill performance model (HELP3). The results show that groundwater pumping leads negative impact to long-term decrease in groundwater levels, particularly in the dry season, while no significant effects of vegetation on groundwater were observed. Moreover, the result showed an average annual groundwater recharge ranging from 20 to 35 mm/a (about 10 to 15 % of the precipitation period 2001–2010), concentrated in the north and southwestern regions (outcrops of permeable/coarse-grained limestone and a major fault zone).

For proper management of groundwater resources, estimation of groundwater recharge is crucial. Information on groundwater recharge is particularly important in dry areas where groundwater is continuously depleting. In this study, groundwater recharge was estimated at two locations in the dry, Barind area of Bangladesh using the applied tracer, water balance (WB) and water-table fluctuation (WTF) methods. In the WTF method, considerations for drinking and irrigation withdrawal were taken. For runoff estimation in the WB method, a modified form of the USDA-SCS method was used. The results revealed that the average yearly recharge at the Nachol location varied from 104.9–195.8 mm/year under different methods, having a mean of 136.1 mm/yr over the methods. At Niamatpur location, the recharge rate varied from 125.1 to 210 mm (9.9 – 15.1% of yearly rainfall) under different methods, having a mean of 157.6 mm/yr. On average, the WTF method produced the lowest estimate of recharge followed by WB method. Based on the local geological and hydrological settings and the suitability/limitations of the methods themselves, the tracer technique may be regarded as a reliable method for the study area. The information on recharge will help the ‘water resource agency’ and ‘policymakers’ to adjust pumping/irrigation schemes, avoid over-exploitation of the groundwater resource, and ensure the long-term sustainability of the resource in the area.

Groundwater recharge estimation is essential for sustainable water management and water supply schemes. In this paper, we review groundwater recharge estimation techniques and identify the appropriate methods by considering India’s hydrological and climatic conditions. Significant components of recharge, factors affecting groundwater recharge, aquifer systems of India, and historical groundwater recharge estimation practices are reviewed. Currently used recharge estimation methods are assessed based on case studies. The most popular estimation methods are studied and compared based on their application in various regions. It is observed that the accuracy of the recharge estimates is largely influenced by false assumptions, the possibility of erroneous measurements, a potential lack of reliable data, and a variety of problems associated with parameter estimation. The suitability of different methods for a region is found to depend on time and space considerations, the objective of the study, hydrogeological condition, and availability of data. In Indian conditions, it is suggested to use water table fluctuation and water balance methods for the recharge estimation, provided that accurate water level measurements are assured.

Book Reviews

Groundwater flow modeling and recharge estimation of heterogeneous aquifer: Applied to Matmata aquifer, southeastern, Tunisia

Estimating the spatial and temporal patterns of groundwater recharge through integrated water balance modeling plays an important role in sustainable groundwater resource management. Such modeling effort is particularly essential for data-scarce regions, such as the Rift Valley Lake basin in the Basement Complex of Ethiopia, which has shallow aquifers, a proliferation of wells, and poor groundwater monitoring networks. A spatially distributed water balance model (WetSpass), along with GIS and remote sensing tools, was used for groundwater recharge estimation for its suitability and efficiency in data-scarce hydrogeological regions. The WetSpass model depicted a very good performance in simulating the groundwater recharge in the Upper Gelana watershed within the Rift Valley Lake basin. The water balance analysis revealed that about 7% of the mean annual rainfall is converted to groundwater recharge, and the remaining rainfall amounts are partitioned into surface runoff (19%) and evapotranspiration (75%). The model simulation outputs are also used to investigate the relative influences of biophysical driving factors on the water balance components. While the land use types had a greater influence on the actual evapotranspiration processes, the soil texture classes were the dominant factors in the surface runoff and groundwater recharge processes in the watershed. The groundwater recharge rates were found to be higher than 400 mm/yr in the central parts (Fisehagenent, Tore, and Gedeb) and lower than 165 mm/yr in the southern parts (Hageremariam) of the watershed. The areal proportions of the low, medium, and high recharging parts of the watershed are, respectively, estimated as 15%, 68%, and 17% of the watershed area. Therefore, the spatial and temporal patterns of groundwater recharge should be taken into consideration in developing a sustainable groundwater resources management plan for the Upper Gelana watershed. Managed aquifer recharge can be adopted in high and medium groundwater recharging parts of the watershed to capture stormwater runoff during the wet season to improve the groundwater supply during dry months. Furthermore, monthly groundwater withdrawals should be regulated according to the spatial and temporal patterns of the groundwater recharge in the watershed.

Due to the unplanned growth of urbanization, industrialization and ever-growing population in Nsukka local government of Enugu State, the groundwater exploitations have increased dramatically. For proper planning and management of groundwater resources, there is need for a reliable estimate of groundwater recharge of the area. In the present study, for the first time, the chloride mass-balance method is adopted to estimate groundwater recharge in the study area. Measurements of chloride in groundwater and rainfall were made during 8-month period of the raining season beginning with the first rain on 5th March 2016 and the last rain on 10th October 2016. The main source of recharge considered was estimated from rainfall. The results are presented in the form of a map showing the spatial distribution recharge rate of the study area, which ranges from 1308.9 to 1683.3 mm/year and the recharge percentage of the total rainfall varies from 81.5 to 95.8%. The study area is characterized by moderate groundwater recharge due to the presence of high permeable underlying lithologies which associated with high porosity. Errors in the estimated recharge rate in work maybe large because of the limited data used in this analysis.

Accurate estimates of infiltration and groundwater recharge are critical for many hydrologic, agricultural and environmental applications. Anticipated climate change in many regions of the world, especially in tropical areas, is expected to increase the frequency of high-intensity, short-duration precipitation events, which in turn will affect the groundwater recharge rate. Estimates of recharge are often obtained using monthly or even annually averaged meteorological time series data. In this study we employed the HYDRUS-1D software package to assess the sensitivity of groundwater recharge calculations to using meteorological time series of different temporal resolutions (i.e., hourly, daily, weekly, monthly and yearly averaged precipitation and potential evaporation rates). Calculations were applied to three sites in Brazil having different climatological conditions: a tropical savanna (the Cerrado), a humid subtropical area (the temperate southern part of Brazil), and a very wet tropical area (Amazonia). To simplify our current analysis, we did not consider any land use effects by ignoring root water uptake. Temporal averaging of meteorological data was found to lead to significant bias in predictions of groundwater recharge, with much greater estimated recharge rates in case of very uneven temporal rainfall distributions during the year involving distinct wet and dry seasons. For example, at the Cerrado site, using daily averaged data produced recharge rates of up to 9 times greater than using yearly averaged data. In all cases, an increase in the time of averaging of meteorological data led to lower estimates of groundwater recharge, especially at sites having coarse-textured soils. Our results show that temporal averaging limits the ability of simulations to predict deep penetration of moisture in response to precipitation, so that water remains in the upper part of the vadose zone subject to upward flow and evaporation.

Estimation of groundwater recharge is essential for efficient groundwater resources management, for domestic uses and irrigation purposes in the study area. The present research entails the assessment of natural groundwater recharge in Terengganu Malaysia. Estimation of recharge by whatever method is usually subjected to a large uncertaintyand errors. However, this research attempt to derive an empirical relationship to determine the groundwater recharge from rainfall based on seasonal groundwater balance studies using the data obtained from 2000-2001 to 2011-2012. This empirical relationship similar to Chaturvedi formula was derived by fitting the estimated values of rainfall recharge, and the corresponding values of rainfall in the monsoon season through the non-linear regression techniques. The result shows that the proportion of variance explained was found to be 89.52 %, the recharge of groundwater commences at P = 15.28 inches and the relative errors was found to range from 3.680 to 46.020%.

Estimation of groundwater recharge and drought severity with varying model complexity

Groundwater has been recognized as an essential water source due to its low pollution susceptibility and large storage capacity. In comparison to surface water, groundwater is relatively safe and reliable. Therefore, it is essential to evaluate groundwater use and its availability for long-term sustainable water management planning. The most important aspects for sustainable water management are estimation of groundwater recharge and water supply schemes. A study was carried out in the Kanpur district to estimate groundwater pumping (GP) and groundwater recharge (GR) from different land cover used in the last 10 years (2009-2019). Assessment of GP and GR were done as per the guidelines of the Ground Water Resource Estimation Methodology–1997 (GEC-97). The results indicated that groundwater is utilized highest as agricultural water consumption then for urban land requirements. Groundwater recharge varied from 30974 ha-m to 39577 ha-m and pumping varied between 12584 ha-m and 47054 ha-m. Since groundwater recharge is higher than its pumping in the study area, it determines that the area is lying under the safe category.