Water Balance Technique Research Articles

The patterns of potential evapotranspiration and seasonal aridity under the change in climate in the upper Blue Nile basin, Ethiopia

Evapotranspiration is one of the determinant components of the hydrological process, highly influenced by climate change due to the increase in atmospheric temperature at global and regional scales. This study was designed to evaluate the extent to which climate change affects the Potential Evapotranspiration (PET) and the consequent Aridity Index (AI) in the high-emission scenario of Representative Concentration Pathways (RCPs) in the Gilgel Abay, Ribb, Gumara, and Megech watersheds using six Global Climate Models in the 2011–2040, 2041–2070, and 2071–2100 relative to the 1971–2000 (baseline period). The average PET is simulated using the Soil Water Assessment Tool (SWAT) model. Penman-Monteith and Hargreaves methods were used in the computation of PET using the water balance technique, and the Hargreaves method was found more efficient in calibration and validation processes. The Aridity Index (AI) of watersheds is calculated using the ratio of precipitation and potential evapotranspiration. The study revealed that the change in annual average PET is showing an increasing pattern in the three time periods, and the highest rate of changes in Megech, Gilgel Abay, Ribb, and Gumara, watersheds are 16.66%, 15.53%, 14.68%, and 13.46%, respectively in the 2071–2100 time period. Seasonally, the highest rate of change in PET is 20.37% (September), 19.29% (April), 17.46% (March), and 17.02% (March) in the Megech, Gilgel Abay, Ribb, and Gumara, respectively. Similarly, the seasonal highest change in Aridity Index (AI) is also likely to be observed in the 2071–2100 in which in the dry season, it accounts –0.303 (March), –0.299 (March), –0.285 (April), and –0.276 (April) in the Ribb, Gumara, Gilgel Abay, and Megech, respectively, whereas in the rainy season, the change is 0.263, 0.258, 0.238, and 0.211 in the Gilgel Abay, Gumara, Ribb, and Megech, respectively. In general, due to the rising atmospheric temperature, the amount of moisture during dry seasons in the headwater catchments of the upper Blue Nile basin is expected to deplete in the 21st century. Therefore, it is highly recommended to use different climate change adaptation mechanisms including adopting suitable physical and biological water conservation techniques to enhance the amount of water stored in the subsurface and joining the groundwater during the rainy season.

Groundwater modeling and estimation of the safe pumping rate for the sustainable use of groundwater resources in Kombolcha town, upper Borkena watershed, Ethiopia

ABSTRACT The rate of groundwater extraction is increasing due to population growth. Balancing pumping rates with natural recharge is necessary for sustainable use. The safe groundwater pumping rate was determined using the groundwater model ModelMuse. To determine the safe pumping rate, 39 borehole data points were gathered and adjusted for 4, 8, and 12 h of pumping scenarios for 50 years in a steady-state pumping condition. The recharge rates in the study area were calculated using four empirical approaches in addition to the water balance method. Of the four empirical methods, the water balance technique provided the most accurate estimates of groundwater recharge, with an estimated average recharge rate of 176.75 mm per year. The ModelMuse model water balance report demonstrated that there was positive storage for all boreholes to be pumped simultaneously under 4- and 8-h pumping rate scenarios, but that there would be a significant drawdown under 12-h pumping from the stress period of 2039–2065, and the summation of inflow and outflow would become negative, indicating that the withdrawal rate is greater than the recharge rate. Thus, the safe pumping rate for Borkena groundwater was calculated to be 975 L/s in 8-h pumping rate scenarios.

Climate variability impact on crop evapotranspiration in the upper East region of Ghana

Ghana's agriculture is primarily rain-fed, making it vulnerable to the impact of climate variability and climate change. This study examined the trends and impact of climatic variability and evapotranspiration on the crop evapotranspiration of selected staple crops across three districts in the Upper East region of Ghana over a 19-year period. Data on agro-climatic conditions (rainfall, temperature, relative humidity, and sunlight) in the Upper East region were obtained from the Ghana Meteorological Agency (GMet) from 2000 to 2018. Given the non-conformity of the response variables to the normality assumption, the Quantile Regression (QR) was employed to examine the impact of climatic variability on different crop evapotranspiration scenarios (low = 10 %, typical = 50 %, and high = 90 %) of the selected crops. The analyzes disclosed a significant difference in crop evapotranspiration between the districts, except for maize, which remained consistent. There was an increase in crop evapotranspiration trend for all, but the maize crop informs the potential improvement of crop evapotranspiration notwithstanding the climatic variability. The study offers a vital insight into the complex dynamics of crop evapotranspiration in response to climatic variability and evapotranspiration. It is recommended, therefore, to consider advances in crop varieties through continuous investment in crop breeding research programmes to improve drought tolerance crops and develop regional water balance techniques.

Climate indices and their variabilities in the state of Pernambuco – Brazil

The climatic indices represent part of the characterization of a given region, being obtained through the water balance and the potential evapotranspiration. The objective is to study the fluctuations and perform the analysis and mapping of the indices of humidity, water and aridity, precipitation and average annual air temperature for the State of Pernambuco using the Climatological Water Balance technique according to the [35]. The data used were average monthly precipitation and monthly averages of air temperatures from 1962 to 2015, these data were estimated using the software, Estima_T, while the precipitation data were acquired from the Agencia Pernambucana de Água e Clima. Temperature reductions occurred in accordance with the displacement of the rainy season and the actions and/or contributions of regional and local effects. Elevation and latitude are the physiographic variables that best explain the monthly and annual temperature variation in the study area.

Assessment of Irrigation Water Loss and Water Balance in the Thenpennaiyaru Basin of Tamil Nadu, India

This study employed a comprehensive technique for the systematic estimate of the water balance in Thenpennaiyaru river basin irrigation systems (TRB-IS) in Tamil Nadu, India. KRP reservoir and Sathanur reservoir in TRB are the primary water sources in the study area. We computed the actual water loss in open canals (e.g., leakage and evaporation). A water balance technique provides for the accounting of various system volume inputs (e.g., water abstraction, imported water, water volume owing to precipitation or surface runoff), authorized consumptions, and water losses in canals and intermediate reservoirs. The proposed methodology enables the evaluation of various water loss components (e.g., evaporation losses, unauthorized uses, metering errors, leakage, and discharges) and the calculation of water loss performance indicators that enable the identification of the most significant water loss problems and provide guidance for managing water losses. The approach is evaluated and implemented using a hybrid irrigation system. Results indicate that discharges in canal systems account for over half of the total volume of water loss, followed by leakage in canals and metering problems. These findings emphasize the need to enhance the everyday operation of these systems and restore their infrastructures.

Quantifying Diyala River basin rainfall-runoff models for normal and extreme weather events

Abstract A variety of methods, including both modeling and non-modeling water balance techniques, are used in this study to estimate water availability allocated for different demands. The area under investigation is the shared Diyala River basin between Iraq and Iran, which is vulnerable to climate change impact and upstream control and aims to enhance watershed management. Two rainfall-runoff models were applied, the Tanh curve model and the modified Tanh curve model for runoff simulation at the Derbendkhan and Hemmrin hydrometric stations. Data from two meteorological stations in Iraq (Khanakin and Sulymania) and one in Iran (Sanandaj) for 20 hydrological years (2000–2020) was used. Some goodness of fit indicators were used to evaluate the reliability of the model outcomes, including the correlation coefficient, the root mean squared error, the mean absolute error, the deviation of runoff volume, and the index of agreement. Statistical analysis shows no statistically significant difference between observed and predicted runoff at all stations in winter, spring, and annual time scales when using the Tanh curve model, or for monthly and extreme wet events when using the modified Tanh curve method. The modified Tanh curve model was more accurate than the Tanh model and applied only to Sulymania and Sanandaj stations, as it required a considerable amount of precipitation in at least semi-humid areas.

Effects of tillage systems on soil water distribution, crop development, and evaporation and transpiration rates of soybean

Tillage practices are known to affect soil water retention, plant available water and, consequently, crop production. Impacts can be determined by assessing soil hydraulic properties and crop characteristics. In this study, three tillage practices were investigated with respect to vertical soil water distribution and development of soybean. A specific focus was set on determining evaporation and transpiration as fractions of evapotranspiration to obtain additional information on water availability and crop water use. The agricultural practices included conventional tillage, reduced tillage (no plow), and no-tillage. The study site was a long-term field experiment under rainfed conditions. The investigations covered a vegetation period of soybean. The measurements comprised weather and soil water monitoring using sensors and manual monitoring of crop development. Evapotranspiration and its components were determined using scintillometer measurements and an isotope-based water balance technique. In the researched vegetation period with limited water availability, the conservative tillage practices showed better water storage, water use, and crop yields compared to the conventional practice. The weekly evaporation and transpiration rates progressed according to the respective canopy development. Thus, delayed plant development of the no-till practice led to extended green cover and productive water use during the late season, where a large part of the precipitation has fallen. The tillage-induced differences of soil hydraulic properties had a substantial impact on soil water distribution, but a comparatively small impact on the soil surface wetness and thus directly on the evaporation rate. The tillage-induced impacts on soil cover by plant residues, however, showed the substantial reduction effect of plant residue cover on evaporation losses. Hence, assessment of evaporation and transpiration rates contributes to the understanding of differences in water productivity and promotes the efficient use of the available water resources.

Water balance technique to optimize the plant population of mango in dry land horticulture

Water balance technique to optimize the plant population of mango in dry land horticulture

Appraisal of groundwater recharge in Neelum watershed (Upper Indus Basin) using geospatial water balance technique

Water availability is important for survival of millions of people living in the Himalayan region of Upper Indus Basin and adequate monitoring system is for better water resources management. In the present study, groundwater recharge appraisals in the Neelum watershed (Upper Indus Basin) were investigated by using water balance and geospatial modeling techniques on monthly time-scale climate data from 1989 to 2015. Results demonstrated that on an average out of total annual rainfall (i.e., 2028 mm), about 46% of the rainfall convert to surface runoff and 35% loss to atmosphere via evapo-transpiration (ET), while the remaining 18% contribute to infiltrate the groundwater recharge. Groundwater recharge enhanced during snow-melt from December to March and the rainfall infiltration increased during July and August months. Similarly, the infiltration ranges 106–177 mm from January to March and 45–51 mm from December to July. The groundwater discharge in the form of oozing from the spring occurred during the remaining six months, which ultimately contributed to the baseflow of the stream. Findings from the study revealed variations in groundwater recharge during the years and hence recommended more hydrological studies to predict future changes in climate and land use for sustainable development of freshwater resources in the Upper Indus Basin.

CLIMATIC ANALYSIS FOR PIRMAM AREA, KURDISTAN REGION, IRAQ

Techniques for water balance are methods of solving major theoretical and practical hydrological problems. The main objectives of this research are analyzing climatic parameters and the climatic conditions to be used in the water balance technique applied in Pirmam area, northern Iraq. The meteorological data of the Pirmam meteorological station during the period 1992–2017 were used to assess the climatic conditions of the study area. The average annual rainfall is 689.2 mm and the evaporation is 1665.9 mm, mean monthly relative humidity, temperature, wind speed, and sunshine were 52.25%, 21.36 oC, 2.26 m/sec, and 8.28 hr/day, respectively. Thornthwait method was used to determine potential evapotranspiration, water surplus and deficit, soil conservation method was used to determine surface runoff, and groundwater recharge based on water balance method. The results indicate that total potential evapotranspiration, water surplus and deficit are 1451.5 mm, 389.84 mm, and 1152.23 mm respectively, and annual runoff equal to 209.6 mm/year. The standardized precipitation index was calculated to characterize meteorological drought on a range of timescales, the average value of is -0.012. Groundwater recharge of the area equal to 209.6 mm/year and groundwater budget is 2.34*105 m3/year. Different methods were like Mather, Unep, and Al-Kubaisi, the results of these classifications show that climate is dry-sub humid according to the first classification, semi-arid according to the second classification, and humid to moist according to the third classification.

Climatic Parameters Analysis of Koysinjaq Meteorological Station, Kurdistan Region, Northern Iraq

The aim of this study was to analyze the climatic data parameters in an interesting catchment, northern Iraq, the Koysinjaq catchment. The climatic conditions were further utilized in the water balance technique. The investigated periods (2000-2019) of meteorological data were used to assess the climatic and drought conditions in Koysinjaq Basin. In terms of water availability, the mean annual rainfall was 595mm and relative humidity was 50.3%, whereas regarding the water losses elements, the total monthly evaporation is 2058.3 mm, temperature, wind speed and sunshine were 22.3 oC, 2 m/sec, and 7.8 hr/day respectively. Kharrufa method was employed to define potential evapotranspiration, and identify periods of water surplus and deficit. The results indicated that total potential evapotranspiration, water surplus and deficit are 2209.04 mm, 258.2 mm, and 1872.4 mm respectively. Different methods were used for climate classification like Mather, Unep, and Al-Kubaisi, the results of these classifications show that climate is dry-sub humid according to the first classification, semi-arid according to the second classification, and humid to moist according to the third classification.

Joint energy and water management scheme for water supply systems in Romania

Keeping in mind the short-term and long-term aims of cost depletion and sustainable development respectively, a joint water and energy management scheme for water supply systems that leads to reduced energy losses is proposed. For water utilities, drinkable water's treatment and pumping and wastewater treatment are the main energy-consuming processes and a proportional part of this energy is wasted with non-revenue water. In Romania, these losses can reach critical levels so highlighting them becomes a crucial aspect in assessing the system's efficiency. This paper presents a scheme that combines energy audit and water balance techniques that can become a tool for both energy auditors and managers, by allowing the quantification of embedded energy of water losses. The methodology is adapted for the conditions in Romania, where data collection and processing is mainly done manually.

Dynamics of crop coefficients for citrus orchards of central India using water balance and eddy covariance flux partition techniques

Accurate quantification of crop water demand and characterizing its temporal variability is essential in evaluating the role of water saving strategies for sustainable production. Representing evapotranspiration (ET) as a proxy to crop water needs is often misleading, particularly during the periods of high non-stomatal exchanges. This study is aimed at modeling crop water requirements for citrus orchards of central India using single and dual crop coefficient approaches. ET fluxes derived from eddy-covariance (EC) technique were used to develop single crop coefficient (Kc) curves at daily, weekly, and seasonal scales. Site-specific Kc values for initial, mid, and late season were found to be 0.43, 0.78, and 0.80 respectively. ET partitioning was done by estimating soil evaporation coefficient (Ke), and basal crop coefficient in the presence of water stress (Ks×Kcb) using soil-water balance (SIMDualKc) and EC flux partitioning (EC FP) methods. SIMDualKc model was calibrated against electrical resistivity tomography (ERT) derived soil water contents (R2 = 0.81, RMSE = 0.021 cm3 cm−3). Energy based flux partitioning was done by considering the correlation between high-frequency water vapour and carbon fluxes and applying flux variance similarity principles. Direct measurement of evaporation (E) and transpiration (T) at four citrus trees (using micro-lysimeters and sap flow meters) was used to assess the performance of two models. Three-stage basal crop coefficients from SIMDualKc and EC FP methods were found to be 0.18, 0.57, 0.63 and 0.26, 0.51, 0.59 respectively. Both methods were effectively partitioning the ET fluxes at daily scale (R2 > 0.5, RMSE < 0.6 mm, NSE > 0.3), however, variability in estimated fluxes between the two methods is high during the initial stage and gradually diminished with time.

Calculating of Groundwater Recharge using Meteorological Water Balance and Water level Fluctuation in Khan Al-Baghdadi Area

Climate and hydrological conditions in any hydrological basin are multi-combined reflection of natural factors of morphology and soil nature, as well as the changing in climate factors that affect directly on hydrological cycle. Water balance techniques are a means of solution of important theoretical and practical hydrological problems, while estimating the physical properties of water-bearing layers is an essential part of groundwater studies. One of the most effective ways of determining these properties is to conduct and analyze aquifer tests. The aim of this research is to compare groundwater recharge in Khan Al-Baghdadi area which located to northwest of Anbar governorate in the west of Iraq, depending on meteorological water balance and calculated hydraulic parameters of groundwater aquifers in order to predict the suitable methods to determine groundwater recharge. Geographical position, elevations, static water levels, depths, thicknesses and maximum yields were carried out during field work. Meteorological parameters of Hit station during the period (1995-2010) was used to calculate water surplus using Thorntwaite formula, while cooper-Jacob and Theis recovery solutions were used to calculate transmissivity and storage coefficient. The result indicate that water surplus was (16.71) mm. divided into (10.13) mm as runoff and (6.58) mm as groundwater recharge. The average annual of groundwater recharge in the area was (41.38) million cubic meters depending on water balance technique, while annual groundwater recharge calculated based hydraulic parameter was (41.51) million cubic meters.

Water use of irrigated almond trees when subjected to water deficits

Recently planted intensive almond plantations may have access to limited water supply due to water scarcity thus, information on almond water use under limited irrigation is needed. Here, the soil water balance was used to assess the consumptive use (ET) of full irrigated, moderately stressed and severely stressed almond trees over a three-year study, as well as the relation between applied water and ET. Sap flow measurements in eight experimental trees were used to obtain independent transpiration (T) measurements. Evaporation from soil (ES) was modelled to estimate tree T from the water balance. Relative consumptive use in the deficit irrigation (DI) treatments largely exceeded the relative applied water, highlighting the need to measure ET in stressed treatments for hydrologic purposes. The moderately stressed treatments (irrigated at 65.5% of full irrigation) consumed 79.0% of maximum evapotranspiration (ET of 897mm), while the severely stressed treatment consumed 63.6% of ETc (ET of 722mm) when applied water was only 39.6% of control. On average, almond ETc approached 1200mm, Seasonal evolution of the transpiration coefficient yielded maximum peak values ranging from 0.99 to 1.08, and minimum peak values of 0.33 attained with a severe deficit irrigation strategy. Transpiration measured by Compensated Heat Pulse-Calibrated Average Gradient sap-flow (x), was compared to water balance T estimates (y), and yielded a very good relation over the three years of study (y=0.90x+4.23, r2=0.81). The sap flow measurements proved to be useful to overcome the limitations of the soil water balance technique, revealing that almond trees were able to extract water from below the monitored depths and suggesting that deep percolation event must have occurred in spring and autumn.

Water productivity of maize in the US high plains

Maize water production functions measured in a 4-year field trial in the US central high plains were curvilinear with 2.0 kg m−3 water productivity at full irrigation that resulted from 12.5 Mg ha−1 grain yields with 630 mm of crop evapotranspiration, ETc. The curvilinear functions show decreasing yield but relatively constant water productivity up to 25% ETc reduction. Water productivity declined rapidly with ETc reductions greater than 25% and was zero at about 40% of full ETc because about 270 mm of ETc was required to produce the first unit of grain yield. These results corroborate those of previous studies that show reduction in irrigated area rather than deficit irrigation will usually provide higher net returns if water consumption (ETc) is limited. Water balance techniques adequately estimated ETc when precision irrigation was carefully scheduled and seasonal precipitation was low. Water productivity relationships based on ETc are more transferable than those based on irrigation water applied.

New Approach For Prediction Groundwater Depletion

Current approaches to quantify groundwater depletion involve water balance and satellite gravity. However, the water balance technique includes uncertain estimation of parameters such as evapotranspiration and runoff. The satellite method consumes time and effort. The work reported in this paper proposes using failure theory in a novel way to predict groundwater saturated thickness depletion. An important issue in the failure theory proposed is to determine the failure point (depletion case). The proposed technique uses depth of water as the net result of recharge/discharge processes in the aquifer to calculate remaining saturated thickness resulting from the applied pumping rates in an area to evaluate the groundwater depletion. Two parameters, the Weibull function and Bayes analysis were used to model and analyze collected data from 1962 to 2009. The proposed methodology was tested in a nonrenewable aquifer, with no recharge. Consequently, the continuous decline in water depth has been the main criterion used to estimate the depletion. The value of the proposed approach is to predict the probable effect of the current applied pumping rates on the saturated thickness based on the remaining saturated thickness data. The limitation of the suggested approach is that it assumes the applied management practices are constant during the prediction period. The study predicted that after 300 years there would be an 80% probability of the saturated aquifer which would be expected to be depleted. Lifetime or failure theory can give a simple alternative way to predict the remaining saturated thickness depletion with no time-consuming processes such as the sophisticated software required.

Impact of wastewater irrigation on soil physico-chemical properties, growth and water use pattern of two indigenous vegetables in southwest Nigeria

The indiscriminate use of wastewater for irrigation as a result of freshwater shortage could impair soil functions and cause environmental pollution. The objective of this study was to evaluate soil physico-chemical properties, growth parameters and water use pattern of two indigenous vegetables irrigated with three kinds of wastewater in southwest Nigeria. The study was a 2×4 factorial (wastewater versus vegetable) pot experiment, laid out in randomized complete block design (RBCD) with three replications in a screen house. The tested vegetables were SM — Eggplant (Solanum macrocarpon) and CA — Spinach (Celosia angentea) while the wastewater treatments were abattoir wastewater (AW), bathroom, laundry wastewater (BW) cassava effluent (CE) and rainwater (RW) as control. The wastewaters were analyzed for physical, chemical and biological properties while the soil samples collected from the field at 0–20cm soil layer and pots at 0–10 and 10–20cm layer were analyzed for physico-chemical properties before and after the experiment, respectively. Soil hydrophobicity was determined using the water-droplet penetration time (WDPT) method, plant growth parameters were monitored every 5days while leaf area was determined shortly before harvest. Consumptive water use was determined using the soil water balance technique. The wastewaters had moderate to very high degree of restriction for use in relation to salinity and sodicity. Except for CE treatment, wastewater irrigation increased the soil pH, Mg, K, Ca, TOC, TN and CEC at harvest. SAR surpassed the threshold value of 6 in the surface layer of CA soil irrigated with BW wastewater. Wastewater irrigation caused the occurrence of soil hydrophobicity, with the highest hydrophobic degree from CE treatment. The plant growth indices showed that the SM vegetable performed better under AW treatment while the CA vegetable performed better under BW treatment compared with RW treatment. The vegetables differed in relation to water use and there was no discernible trend among the different wastewater treatments as regards the temporal distribution of the consumptive water use. The CE wastewater had the most negative impact on both soil function and plant growth. The study showed that wastewater resources are valuable because of improvement of soil fertility and enhanced crop growth compared with rainwater, however they need to be managed with caution, preferably treatment, before reused in relation to soil functions and crop quality.

English

The objective of this study was to test the utility of a spatial explicit water balance technique in assessing the rainwater harvesting potential for crop production to design food security strategies in the Bugesera District. The district was delineated into 19 catchments through the hydroprocessing algorithm in ILWIS using the SRTM 90 m DEM, and runoff, a proxy of the potential rainwater harvest, was computed using the Natural Resources Conservation Service Curve Number method. Results from the analyses indicate that based on the average antecedent moisture condition, the average daily runoff that can be collected out of Bugesera district is approximately 1,320 x 106 m3/day. Allowing a third of this runoff for environmental requirements and evaporation losses, the amount of rainwater that could be used for crop production has been estimated to be 880 x 106 m3 per day. By using the CSIRO&rsquo;s precision weighing systems to measure water use by various crops and yield from the crops, the amount of harvested rainwater has the potential of producing between 398 x 103 to 531 x 103 tones of paddy rice and 1,390 x 103 to 1,620 x 103 tones of maize. This potential crop yield can significantly improve food security in the Bugesera district. It was therefore concluded that rainwater harvesting for crop production is a viable option in Bugesera district and further implantation modalities should be explored. &nbsp; Key words: Rainwater harvesting, natural resources conservation service (NRCS) curve number, crop production, digital elevation model (DEM), catchment delineation, Bugesera District.&nbsp

Assessment and estimation of groundwater recharge for a catchment located in highland tropical climate in central Ethiopia using catchment soil–water balance (SWB) and chloride mass balance (CMB) techniques

Two commonly applied groundwater recharge estimation techniques, namely soil–water balance (SWB) and the chloride mass balance (CMB) methods, were applied and compared to quantify and analyse groundwater recharge in the Akaki catchment, located in central Ethiopia. The semi-distributed SWB method estimated natural groundwater recharge at 105 mm/a (10 % of the mean annual areal precipitation, MAAP). The chloride mass balance method applied to the same catchment estimated mean annual groundwater recharge at 273 mm/a (25 % of the MAAP). The SWB recharge value is much less than the recharge estimated by CMB method, highlighting the importance of preferential flow path recharge mechanism which is not captured by the SWB method. In situ permeability measurements undertaken as part of this research and an earlier investigation based on environmental isotopes have demonstrated that the catchment gets recharged both from direct and preferential flow recharge mechanisms which explains the discrepancy between recharge estimated through the two methods. Therefore, SWB model result which only takes into consideration the piston-type flow recharge mechanism should be taken as the minimum possible groundwater recharge for the catchment characterized by fractured aquifers. The mean recharge estimate from the two methods represents the maximum possible recharge estimate for the catchment investigated. Although calibration of the recharge estimates was not possible, the SWB recharge estimate is found to be highly sensitive to changes in precipitation input. The findings of this research underline the fact that multiple recharge estimation methods are important to understand and capture possible recharge mechanisms and to reach to an acceptable recharge estimate.