Aquifer Depletion Research Articles

Effects of instantaneous groundwater availability on irrigated agriculture and implications for aquifer management

Groundwater is an important input for agricultural production in many parts of the world. Aquifer depletion has been shown to affect the rate that groundwater can be extracted from an aquifer. In this paper, we develop an analytical framework that accounts explicitly for the effects of limited instantaneous groundwater extraction rate (well capacity) on a producer's irrigation decisions. We show that limited well capacities can affect the producer’s groundwater use and profit. We draw three important insights from these findings. First, we demonstrate that the price elasticity of demand for groundwater is higher for lower well capacities. Second, farmers’ irrigation decisions are non-monotonic with respect to well capacity and climate conditions. Under a drier climate, producers with greater well capacities increase their groundwater use, and producers with lower well capacities reduce their water use. Third, through numerical analysis, we show that considering spatial heterogeneity in well capacities is important for estimating the cost-effectiveness and distributional impacts of groundwater management policies. Our results shed new light on the importance of extraction capacity for groundwater management policies and the potential impacts of climate change on agricultural production.

A Parametric Numerical Analysis of Factors Controlling Ground Ruptures Caused by Groundwater Pumping

AbstractA modeling analysis is used to investigate the relative susceptibility of various hydrogeologic configurations to aseismic rupture generation due to deformation of aquifer systems accompanying groundwater pumping. An advanced numerical model (GEPS3D) is used to simulate rupture generation and propagation for three typical processes: (i) reactivation of a preexisting fault, (ii) differential compaction due to variations in thickness of aquifer/aquitard layers constituting the aquifer system, and (iii) tensile fracturing above a bedrock ridge that forms the base of the aquifer system. A sensitivity analysis is developed to address the relative importance of various factors, including aquifer depletion, aquifer thickness, the possible uneven distribution and depth below land surface of the aquifer/aquitard layers susceptible to aquifer‐system compaction, and the height of bedrock ridges beneath the aquifer system which contributes to thinning of the aquifer system. The rupture evolution is classified in two occurrences. In one, the rupture develops at either the top of the aquifer or at land surface and does not propagate. In the other, the developed rupture propagates from the aquifer top toward the land surface and/or from the land surface downward. The aquifer depth is the most important factor controlling rupture evolution. Specifically, the probability of a significant rupture propagation is higher when the aquifer top is near land surface. The numerical results are processed by a statistical regression analysis to provide a general methodology for a preliminary evaluation of possible ruptures development in exploited aquifer systems susceptible to compaction and accompanying land subsidence. A comparison with a few representative case studies in Arizona, USA, China, and Mexico supports the study outcomes.

Long run optimization of landscape level irrigation through managed aquifer recharge or expanded surface reservoirs

Decades of efforts to reduce groundwater overdraft through investment in irrigation efficiency has, in many cases, failed to reduce aquifer depletion. This is one reason for greater attention to water supply augmentation efforts through the capture of surface water during high flow events for managed aquifer recharge (MAR) or additional surface storage. We use a landscape level model to examine the optimal interaction among MAR, surface reservoir storage, crop choice, and groundwater conservation policies in Eastern Arkansas. We find the cost of MAR water must be less than half the average groundwater pumping cost to increase the aquifer level. Increases in irrigation intensive crops mean that only a fraction of the recharged water raises groundwater levels. We observe that policies to conserve groundwater, such as a pumping cap or tax, are more cost-effective for society with a lower cost of MAR water.

Causes, consequences and coping strategies of land degradation: evidence from Ethiopia

T his review paper aims to review on the causes and consequences of land degradation in Ethiopia. The results from different literatures indicate that the major factors that cause land degradation in Ethiopia are: clearing woodland for agriculture , repeated cultivation, removal of residuals and dungs, single cropping, extraction of wood, , population growth, deforestation, soil erosion, low technology, inadequate extension services, political instability, cultivation on steep slopes, overgrazing, traditional way of cultivation, heavy wind, high intensity of rainfall, drought and landslides, absence of all-inclusive land use and lack of land use plans developed. On the other hand, the depletion of forests and vegetation, loss in water resources, decrease in the quality and quantity of livestock, enhancing the unemployment rate and out-migration, conflict between pastoralists, food insecurity, deceasing of soil fertility and arable land, reduction of agricultural productivity, increasing price of farm inputs, reduction of plants grown, depletion of aquifers, loss of biodiversity, reduction of potable water, shortages of timber, climate change and desertification are the major consequences of land degradation in Ethiopia. Afforestation, Reforestation, terracing, crop rotation, mixed cropping, irrigation schemes and traditional soil conservations are among the coping strategies that Ethiopian farmers are using. To overcome this problem, strengthening the teamwork among policy makers, GOs/NGOs, local communities, research institutes and the mass media are the key agents that must take these responsibilities.

Four-dimensional filtering of InSAR persistent scatterers elucidates subsidence induced by tunnel excavation in the Sri Lankan highlands

During construction of the Uma Oya Multipurpose Development Project, excavation of a headrace tunnel through highly tectonized metamorphic rock was slowed by repeated major water ingress events. In total, these events resulted in an estimated aquifer depletion of over 9 million m3, causing widespread surface subsidence. Persistent scatterer (PS) time series analysis of interferometric synthetic aperture radar (InSAR) scenes acquired by Sentinel-1 between July 28, 2016, and January 7, 2018, has revealed an ∼15 km2 area of subsidence near reported water ingress locations, with a maximum line-of-sight subsidence value of 4.3 cm. A four-dimensional (4-D) filtering method based on averaging spatial and temporal pixel neighbors was applied to the unwrapped PS pixels, significantly reducing noise from sources that appear randomly in spatial and temporal domains and increasing the ability to accurately identify the onset of subsidence and track surface volume loss over time. A maximum average subsidence rate of 0.15 mm / day coincides with maximum tunnel discharge measurements, indicating that rock mass consolidation occurred as a result of rapid pore-pressure drawdown within an interconnected discontinuity network and led to fracture closure. The observed subsidence is punctuated by localized maxima and extends in a northwest–southeast orientation, suggesting that the extent of subsidence is governed by previously mapped structural trends of similar orientations. These results highlight the value of the 4-D filtering approach in processing InSAR PS data to help determine the magnitude and extent of surface subsidence.

A pathway of global food supply adaptation in a world with increasingly constrained groundwater

Many of the world's major freshwater aquifers are being exploited unsustainably, with some projected to approach environmentally unsafe drawdown limits within the 21st century. Given that aquifer depletion tends to occur in important crop producing regions, the prospect of running dry poses a significant threat to global food security. Here we use the Global Change Assessment Model (GCAM) to explore the response of land use and agriculture sectors to severe constraints on global water resources. We simulate a scenario in which a number of important groundwater aquifers become depleted to the point where further water withdrawal is unviable, either due to excessive extraction costs or environmental limits being reached. Results are then benchmarked against a scenario that neglects constraints on water withdrawals. We find that groundwater depletion and associated water price increases drive two distinct responses in the agriculture sector: an expansion of rain fed agriculture, and a shift in irrigated crop production toward regions with cheaper water resources. Losses in crop production are most pronounced in water stressed regions where groundwater is being depleted unsustainably to meet irrigation demands—namely northwest India, Pakistan, the Middle East, western United States, Mexico, and Central Asia. While these results highlight substantial risks for the affected regional agricultural economies, we show that modest changes in irrigation and location of crop growth, in a world with frictionless trade, could ensure global food demands are met despite severe water constraints.

An Integrated Approach Toward Sustainability via Groundwater Banking in the Southern Central Valley, California

AbstractIntensive groundwater withdrawals in California have resulted in depletion of streams and aquifers in some regions. Agricultural managed aquifer recharge (Ag‐MAR) initiatives have recently been piloted in California to mitigate the effects of unsustainable groundwater withdrawals. These initiatives rely on capturing wet‐year water and spreading it on large areas of irrigated agricultural lands to enhance recharge to aquifers. While recharge studies typically consider local effects on aquifer storage, few studies have investigated Ag‐MAR benefits and challenges at a regional scale. Here we used the Integrated Water Flow Model, to evaluate how Ag‐MAR projects can affect streamflows, diversions, pumping, and unsaturated zone flows in the southern Central Valley, California. We further tested the sensitivity of three different spatial patterns of Ag‐MAR, each chosen based on different thresholds of soil suitability, on the hydrologic system. This study investigates how the distribution of Ag‐MAR lands benefit the regional groundwater system and other water balance components. The results suggest that Ag‐MAR benefits vary as a function of the location of Ag‐MAR lands. Stream‐aquifer interactions play a crucial factor in determining the ability to increase groundwater storage in overdrafted basins. The results also indicate that Ag‐MAR projects conducted during the November–April recharge season have implications for water rights outside of the Ag‐MAR season. If not properly monitored, Ag‐MAR can cause a rise of groundwater table into the root zone, negatively impacting sensitive crops. Our work also highlights the benefits of using an integrated hydrologic and management model to evaluate Ag‐MAR at a regional scale.

Energy consumption due to groundwater pumping for irrigation in the North China Plain

Irrigated agriculture consumes a large amount of groundwater resources with a huge energy requirement, and this has seriously restricted the development of green and efficient agriculture in China. However, recent studies on energy consumption for irrigation focus mainly on individual irrigation systems or single wells, and few spatial-temporal energy assessments have been carried out at regional scale. This is needed for effective management of regional energy consumption for groundwater utilization. Based on single-well pumping method, a distributed energy consumption model for groundwater irrigation (DPE_GI) was proposed in this study. The North China Plain (NCP) was selected as the research area, which is a typical groundwater irrigated area and has severe issues with aquifer depletion. The results showed that the average annual energy consumption for groundwater pumping was 13.67 billion kW h, and the energy consumption per area was 1122.4 kW h hm−2 under the winter wheat - summer maize rotation system in NCP. Current groundwater pumping energy consumption in the NCP is 2.9 times of the initial value in 1986, and the NCP has already become the world's largest energy consumer for groundwater irrigation. Due to the uncertainty of precipitation, energy consumption for irrigation fluctuates per growing season. Groundwater level also impacts energy consumption. Popularizing water-saving irrigation technology such as drip or sprinkler irrigation, changing cropping systems and habits can effectively reduce energy consumption for irrigation.

The adoption rate of efficient irrigation practices and the consequences for aquifer depletion and further adoption

The rate of adoption of efficient irrigation practices influences the return on investment from those practices and affects how much, and even whether, aquifer conservation occurs. A spatial-dynamic programming model for an agricultural landscape indicates that as the rate of adoption increases, the return on investment gradually decreases as groundwater levels rise in Eastern Arkansas, USA. The model results also show that slow adoption can increase aquifer depletion because there is a switch to irrigation intensive crops, but fast adoption can conserve the aquifer because a larger proportion of the crops use less irrigation water. Even the fastest adoption rate should not dissuade future adoption because the return on investment in the efficient irrigation practices remains high. At low adoption rates, a subsidy of efficient irrigation practices for the least irrigation intensive crop is almost as cost-effective for groundwater conservation as a tax on well pumping. At high adoption rates, only a tax on well pumping is very cost-effective.

Mapping QTLs and Identification of Genes Associated with Drought Resistance in Sorghum.

Water limits global agricultural production. Increases in global aridity, a growing human population, and the depletion of aquifers will only increase the scarcity of water for agriculture. Water is essential for plant growth and in areas that are prone to drought, the use of drought-resistant crops is a long-term solution for growing more food for more people with less water. Sorghum is well adapted to hot and dry environments and has been used as a dietary staple for millions of people. Increasing the drought resistance in sorghum hybrids with no impact on yield is a continual objective for sorghum breeders. In this review, we describe the loci, quantitative trait loci (QTLs), or genes that have been identified for traits involved in drought avoidance (water-use efficiency, cuticular wax synthesis, trichome development and morphology, root system architecture) and drought tolerance (compatible solutes, pre- and post-flowering drought tolerance). Many of these identified genes and QTL regions have not been tested in hybrids and the effect of these genes, or their interactions, on yield must be understood in normal and drought-stressed conditions to understand the strength and weaknesses of their utility.

Policy measures for reducing aquifer depletion in a context of climate change: the case of the coastal area of Cap-Bon

Groundwater resources are critically important for irrigated agriculture in Tunisia. However, excessive irrigation extractions where groundwater is slowly renewed are causing a widespread depletion of the aquifer systems, with the impacts of climate change expected to further exacerbate this problem. These circumstances call for the development of methodologies and analyses that can support the design of sustainable groundwater management policies. This paper presents a hydro-economic mathematical programming model that is used to evaluate the effects of different policy measures for reducing aquifer depletion in the Cap-Bon region of Tunisia. Three policies have been evaluated: a quota defining the maximum quantity of groundwater extractions, environmental taxation, and supply expansion with subsidized desalinated seawater. Overall, results highlight the economic and social tradeoffs among these different policy choices and the challenges facing the implementation of sustainable groundwater management in Tunisia. More specifically, results show the advantages of using subsidized desalinated seawater compared to the other two policy alternatives in terms of the value of agricultural production, farmers’ profits, and employment, despite of its sizeable budgetary burden.

Assessing the trade-off between shallow groundwater conservation and crop production under limited exploitation in a well-irrigated plain of the Haihe River basin using the SWAT model

Groundwater overdraft due to extensive irrigation has led to a shallow aquifer depletion crisis in the Haihe River basin. Quantitative simulation of the variations in shallow groundwater and crop yield under different conditions of limited exploitation using a distributed hydrological model is important in the well-irrigated plain of this basin. Based on multiple modeling experiments by a modified Soil and Water Assessment Tool (SWAT) model, three limited irrigation schemes for winter wheat (Triticum aestivum L.) were selected as simulation scenarios. The simulated results using the SWAT model showed that under scenario 1 (applying two rounds of irrigation corresponding to the jointing and heading stages of winter wheat), the average rate of decline in the shallow groundwater table was approximately 2/3 of that under the basic scenario (current irrigation schedule), but the winter wheat yield decreased by 13% compared with the basic scenario. Under scenario 2 (applying one round of irrigation at the jointing stage of winter wheat), the average rate of decline in the shallow groundwater table was approximately 1/4 of that under the basic scenario, but the reduction in the winter wheat yield compared with the basic scenario increased to 28%. The amount of overexploited shallow groundwater in the cropland area decreased from 17.5 × 108 m3 a−1 (under the basic scenario) to 11.0 × 108 m3 a−1 under scenario 1 and 4.5 × 108 m3 a−1 under scenario 2. Under scenario 3 (rain-fed conditions during the winter wheat season), the regional variation in the shallow groundwater table shifted to a recovery trend with an average rate of 0.22 m a−1, which was equivalent to restoring 3.5 × 108 m3 a−1 of shallow aquifer storage in the cropland area. However, the reduction in the winter wheat yield compared with the basic scenario reached 54% under the rain-fed scheme. Considering the trade-off between groundwater conservation and crop production under limited exploitation, linear programming was used to optimize the irrigation schedule at the subbasin scale. As a result, to satisfy the constraint of stopping groundwater drawdown, the average minimal reduction in the winter wheat yield would be 42% under the optimal irrigation schedule. By contrast, to satisfy the constraint of restricting the reduction in the crop yield to within the threshold required to maintain winter wheat self-sufficiency, the minimal rate of decline in the shallow groundwater table would be 0.26–0.52 m a−1 under the optimal irrigation schedule. In addition, the uncertainty in the simulated shallow groundwater variation in this study was acceptable, indicating that the above assessments could provide reasonable references for regional groundwater management.

Towards Quantifying the Likelihood of Water Resource Impacts from Unconventional Gas Development.

Gas production from unconventional reservoirs has led to widespread environmental concerns. Despite several excellent reviews of various potential impacts to water resources from unconventional gas production, no study has systematically and quantitatively assessed the potential for these impacts to occur. We use empirical evidence and numerical and analytical models to quantify the likelihood of surface water and groundwater contamination, and shallow aquifer depletion from unconventional gas developments. These likelihoods are not intended to be exact. They provide a starting point for comparing the probabilities of adverse impacts between types of water resources and pathways. This analysis provides much needed insight into what are "probable" rather than simply "possible" impacts. The results suggest that the most likely water resource impacts are surface water and groundwater contamination from spills at the well pad, which can be as high as 1 in 10 and 1 in 100 for each gas well, respectively. For wells that are hydraulically fractured, the likelihood of contamination due to inter-aquifer leakage is 1 in 106 or lower (dependent on the separation distance between the production formation and the aquifer). For gas-bearing formations that were initially over-pressurized, the potential for contamination from inter-aquifer leakage after production ceases could be as high as 1 in 400 where the separation between gas formation and shallow aquifer is 500 m, but will be much lower for greater separation distances (more characteristic of shale gas).

Simulating Crop-Water Production Functions Using Crop Growth Models to Support Water Policy Assessments

Crop-water production functions are important tools for quantifying effects of water scarcity and climate change on agricultural production, and are also widely used within hydro-economic models to support design of inter-sectoral water management policies. Here, we introduce a new methodology for simulating crop-water production functions using process-based crop growth models, which captures explicitly the interacting effects of farmers' intraseasonal irrigation decision-making, stochastic weather conditions, and physical and socio-economic water supply constraints on seasonal crop yield response to water. Through a case study application for groundwater irrigated corn production in the Texas High Plains, we demonstrate that constraints to irrigation scheduling caused by aquifer depletion, combined with farmers' limited foresight of future weather conditions, have significant impacts on estimated seasonal crop-water production functions. Our results highlight that the failure to account for these factors fully in previous simulation approaches will lead to errors in estimates of the impacts of groundwater depletion on farmers' future resilience to drought and climate change. Our proposed simulation methodology is generalizable to different production systems or crop growth models, and provides a tool for assessing how economic benefits derived from irrigation vary spatially and temporally due to heterogeneity in biophysical conditions and irrigation practices.

Monitoring Groundwater Storage Changes Using the Gravity Recovery and Climate Experiment (GRACE) Satellite Mission: A Review

The Gravity Recovery and Climate Experiment (GRACE) satellite mission, which was in operation from March 2002 to June 2017, was the first remote sensing mission to provide temporal variations of Terrestrial Water Storage (TWS), which is the sum of the water masses that were contained in the soil column (i.e., snow, surface water, soil moisture, and groundwater), at a spatial resolution of a few hundred kilometers. As in situ level measurements are generally not sufficiently available for monitoring groundwater changes at the regional-scale, this unique dataset, combined with external information, is widely used to quantify the interannual variations of groundwater storage in the world’s major aquifers. GRACE-based groundwater changes revealed significant aquifer depletion over large regions, such as the Middle East, the northwest India aquifer, the North China Plain aquifer, the Murray-Darling Basin in Australia, the High Plains, and the California Central Valley aquifers in the United States of America (USA), but were also used to estimate groundwater-related parameters such as the specific yield, which relates groundwater level to storage, or to define the indices of groundwater depletion and stress. In this review, the approaches used for estimating groundwater storage variations are presented along with the main applications of GRACE data for groundwater monitoring. Issues that were related to the use of GRACE-based TWS are also addressed.

Assessing groundwater availability and the response of the groundwater system to intensive exploitation in the North China Plain by analysis of long-term isotopic tracer data

The use of isotope tracers as a tool for assessing aquifer responses to intensive exploitation is demonstrated and used to attain a better understanding of the sustainability of intensively exploited aquifers in the North China Plain. Eleven well sites were selected that have long-term (years 1985–2014) analysis data of isotopic tracers. The stable isotopes δ18O and δ2H and hydrochemistry were used to understand the hydrodynamic responses of the aquifer system, including unconfined and confined aquifers, to groundwater abstraction. The time series data of 14C activity were also used to assess groundwater age, thereby contributing to an understanding of groundwater sustainability and aquifer depletion. Enrichment of the heavy oxygen isotope (18O) and elevated concentrations of chloride, sulfate, and nitrate were found in groundwater abstracted from the unconfined aquifer, which suggests that intensive exploitation might induce the potential for aquifer contamination. The time series data of 14C activity showed an increase of groundwater age with exploitation of the confined parts of the aquifer system, which indicates that a larger fraction of old water has been exploited over time, and that the groundwater from the deep aquifer has been mined. The current water demand exceeds the sustainable production capabilities of the aquifer system in the North China Plain. Some measures must be taken to ensure major cuts in groundwater withdrawals from the aquifers after a long period of depletion.

Germination, physiological and biochemical responses of acacia seedlings (Acacia raddiana and Acacia tortilis) to petroleum contaminated soils.

Along the arid Arava, southern Israel, acacia trees (Acacia raddiana and Acacia tortilis) are considered keystone species. Yet they are threatened by the ongoing aquifer depletion for agriculture, the conversion of natural land to agricultural land, seed infestation by bruchid beetles, and the reduction in precipitation level in the region. In the acacia dominated Evrona reserve (southern Arava), adding to these threats are recurrent oil spills from an underground pipeline. We report here a study of the effects of contaminated soils, from a recent (December 2014) and a much older (1975) oil spills. The effects of local petroleum oil-contaminated soils on germination and early growing stages of the two acacia species were studied by comparisons with uncontaminated (control) soils from the same sites. For both acacia species, germination was significantly reduced in the 2014 oil-contaminated soils, whereas delayed in the 1975 oil-contaminated soil. There was no significant effect of oil volatile compounds on seed germination. At 105 days post transplanting (DPT), height, leaf number, stem diameter, and root growth were significantly smaller in the oil-contaminated soils. While photosynthetic performance (quantum yield of photosystem II) did not differ considerably between treatments, reductions of chlorophylls content and protein content were found in seedlings growing in the contaminated soils. Significant increases in superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities were found in roots of seedlings growing in oil-contaminated soils. These results demonstrate that seed germination and seedling growth of both acacia species were strongly restricted by oil contamination in soils, from both recent (2014) and a 40-year old (1975) oil spills. Such long-term effects of oil spills on local acacia seedlings could shift the structure of local acacia communities. These results should be taken into account by local authorities aiming to clean up and restore such polluted areas.

Aquifer Depletion in the Lower Mississippi River Basin: Challenges and Solutions

AbstractThe Lower Mississippi River Basin (LMRB) is an internationally‐important region of intensive agricultural crop production that relies heavily on the underlying Mississippi River Valley Alluvial Aquifer (MRVAA) for irrigation. Extensive irrigation coupled with the region’s geology have led to significant aquifer decline. The response to the decline has been multi‐faceted. Research related to three responses are highlighted: innovation in rice irrigation, on‐farm reservoirs, and managed aquifer recharge. Irrigated rice grown in Arkansas, which is nearly 50% of annual U.S. rice production, accounts for a significant portion of aquifer withdrawal. As a result, strategies for using less water while maintaining rice yields are being developed. The Rice Stewardship Partnership (RSP) began in 2015 and aims to improve irrigation management in rice lands of the LMRB. Early results from the RSP are presented. Secondly, on‐farm reservoir‐tailwater recovery systems (R‐TWRS) are increasingly used to store abundant surface water in the LMRB. Over 700 R‐TWRS are currently used in rice producing areas of Arkansas. The confining clay layer that overlies the MRVAA in many locations limits rates of aquifer recharge. Locations where the confining layer is thin or non‐existent may provide opportunities for artificial (i.e., managed) recharge. A 10‐m deep excavation pit from a highway project provided an opportunity to measure infiltration rates of the uppermost section of the alluvial aquifer. Findings from this and other studies are used to demonstrate how conservation, off‐season rainfall capture and storage, and managed recharge are being investigated as means to reduce the on‐going decline of the alluvial aquifer that is both economically and ecologically important to the LMRB.

Assessing Irrigation Aquifer Depletion: Introduction

Assessing Irrigation Aquifer Depletion: Introduction

The groundwater budget: A tool for preliminary estimation of the hydraulic connection between neighboring aquifers

Groundwater management authorities usually use groundwater budget calculations to evaluate the sustainability of withdrawals for different purposes. The groundwater budget calculation does not always provide reliable information, and it must often be supported by further aquifer monitoring in the case of hydraulic connections between neighboring aquifers.The Riardo Plain aquifer is a strategic drinking resource for more than 100,000 people, water storage for 60 km2 of irrigated land, and the source of a mineral water bottling plant. Over a long period, the comparison between the direct recharge and the estimated natural outflow and withdrawals highlights a severe water deficit of approximately 40% of the total groundwater outflow. A groundwater budget deficit should be a clue to the aquifer depletion, but the results of long-term water level monitoring allowed the observation of the good condition of this aquifer. In fact, in the Riardo Plain, the calculated deficit is not comparable to the aquifer monitoring data acquired in the same period (1992–2014). The small oscillations of the groundwater level and the almost stable streambed spring discharge allows the presumption of an additional aquifer recharge source.The confined carbonate aquifer locally mixes with the above volcanic aquifer, providing an externally stable recharge that reduces the effects of the local rainfall variability.The combined approach of the groundwater budget results and long-term aquifer monitoring (spring discharge and/or hydraulic head oscillation) provides information about significant external groundwater exchanges, even if unidentified by field measurements, and supports the stakeholders in groundwater resource management.