Groundwater Pumping Research Articles

Toward field-scale groundwater pumping and improved groundwater management using remote sensing and climate data

Groundwater overdraft in the western United States has prompted water managers to develop groundwater management plans that include mandatory reporting of groundwater pumping (GP). However, most irrigation systems in this region are not equipped with irrigation water flow meters to record GP and performing quality control of the available metered GP data is difficult due to the scarcity of reliable secondary GP estimates. We hypothesize that Landsat-based actual evapotranspiration (ET) estimates from OpenET can be used to predict GP and aid in quality control of the metered GP data. The objectives of this study are to: 1) pair OpenET estimates of consumptive use (Net ET, i.e., actual ET less effective precipitation) and metered annual GP data from Diamond Valley, Nevada, and Harney Basin, Oregon; 2) evaluate linear regression and machine learning models to establish the GP vs Net ET relationship; and 3) compare GP estimates at the field- and basin-scales. Results from using a bootstrapping technique showed that the mean absolute errors and root mean square errors for field-scale GP depth are ∼11 % and ∼14 % across Diamond Valley and Harney Basin based on the OpenET ensemble mean, which showed the highest skill among all the OpenET ET models. Moreover, the regression models explained 50 %-70 % variance in GP depth and ∼90 % variance in GP volumes. Our GP volume estimates are also within 7 % and 17 % of the total reported and measured volumes in Diamond Valley and Harney Basin, respectively, and the estimated average irrigation efficiency of 87 % aligns with known center-pivot system efficiencies. Additionally, the OpenET ensemble proves to be useful for identifying discrepancies in metered GP data, which are subsequently flagged as outliers. Results from this study illustrate usefulness of satellite-based ET estimates for estimating GP and metered GP data quality control and have the potential to help estimate historical GP.

Land surface response to groundwater drawdown and recovery in Taiyuan city, Northern China, analyzed with a long-term elevation change measurements from leveling and multi-sensor InSAR

In recent years, a comprehensive program of groundwater management was adopted in Taiyuan city, Northern China, with the aim to prevent the lowering of groundwater level and manage land subsidence due to excessive groundwater pumping in the past decades. Groundwater recovery has been observed in this city following the termination of groundwater pumping. While the link between land subsidence and groundwater pumping is well documented, how the land surface responds to the recovery of groundwater has not been studied in detail. In this study, we analyzed the leveling data from 1956 to 2000 to investigate changes in ground elevation in response to groundwater drawdown prior to the termination of groundwater pumping and combined them with InSAR (Interferometric Synthetic Aperture Radar) displacement data during 2003–2020 to evaluate the effect of groundwater recharge after the termination of groundwater pumping. A method was proposed to merge InSAR time series of displacement derived from multiple satellites (ENVISAT, COSMO-SkyMed, TerraSAR-X, and Sentinel-1) to achieve a consistent, long-term continuous deformation. We found that previous groundwater depression cones in Taiyuan (Xizhang, Wanbailin, Wujiabao, and Xiayuan) have turned into groundwater recovery and the corresponding subsidence centers have switched to land uplift. The subsidence center of Xizhang, north of Taiyuan city, experienced a total subsidence of 749 mm by Aug 2003; it then turned into uplift with an amount of rebound of 9.2 % of previous subsidence by the end of 2020. In central area of Taiyuan, the cumulated subsidence is 1127 mm in Wanbailin, 1817 mm in Xiayuan, and 3343 mm in Wujiabao. Beginning in Aug 2010, they all turned into land uplift, with a rebound of 7.9 %, 4.8 % and 3.6 % of the previous subsidence in each center, respectively. An analysis of the correlation between groundwater level and ground displacement suggests that the ground uplift is related to the poro-elastic rebound mechanism in the porous aquifer system, which is caused by the rise in pore pressure with groundwater recovery, and the amount of subsidence/uplift is controlled by the stratigraphic properties. The adverse impacts on the built environment due to the rising groundwater level were discussed. The findings improve our understanding of anthropogenic ground deformation in complex urban aquifers influenced by groundwater pumping and recharge and provides essential information that can contribute to future groundwater management and groundwater-related hazard mitigation over the Taiyuan city.

Effects of groundwater pumping on pore water flow and salt transport in tide‐controlled unconfined coastal aquifers

AbstractUnconfined coastal aquifers are a main pathway for land‐sourced solutes to enter the oceans. The migration of these solutes in aquifers is highly affected by the groundwater flow and salt transport processes, which are, to a great extent, controlled by tides. While many studies have examined how tidal oscillations would influence the subsurface hydrodynamics in coastal aquifers, most of them ignored the potential impact of groundwater pumping, a common practice in coastal areas to satisfy the demand for freshwater. This study, by means of laboratory experiments and numerical simulations, explored the combined effects of tides and groundwater pumping on the pore water flow and salinity distributions in an unconfined coastal aquifer. The results show that, in a tide‐controlled aquifer, the addition of groundwater pumping would exacerbate the degree of seawater intrusion and lead to wider spreading and deeper penetration of the upper saline plume. Moreover, groundwater pumping would enhance the tide‐driven circulation in the upper saline plume and weaken the density‐driven circulation in the saltwater wedge, ultimately leading to the reduction in total submarine groundwater discharge. These findings may promote a deep insight into the complex coastal groundwater systems experiencing human activities, and provide guidance for better evaluating the environmental impact of groundwater pumping.

Summer Monsoon Drying Accelerates India's Groundwater Depletion Under Climate Change

AbstractGroundwater in north India remains a vital food and water security resource for more than one billion people. Both summer monsoon drying, and winter warming pose considerable challenges for rapidly declining groundwater. However, their impacts on irrigation water demands and groundwater storage under the observed and projected future climate remain unexplored. Using in situ observations, satellite data, and a hydrological model that considers the role of irrigation and groundwater pumping, we show that summer monsoon drying and winter warming accelerate groundwater depletion in north India during the observed climate, which will continue in the projected future climate. Summer monsoon precipitation has significantly (P‐value = 0.04) declined (∼8%) while winters have become warmer in north India during 1951–2021. Both satellite (GRACE/GRACE‐FO) and hydrological model‐based estimates show a rapid groundwater depletion (∼1.5 cm/year) in north India with a net loss of 450 km3 of groundwater during 2002–2021. The summer monsoon drying followed by winter warming cause a substantial reduction in groundwater storage due to reduced groundwater recharge and enhanced pumping to meet irrigation demands. Summer monsoon drying and winter warming will continue to affect groundwater storage in north India in the future. For instance, summer monsoon drying (10%–15% deficit for near‐far periods) followed by substantial winter warming (1–4°C) in the future will further accelerate groundwater depletion by increasing (6%–20%) irrigation water demands and reducing groundwater recharge (6%–12%). Groundwater sustainability measures including reducing groundwater abstraction and enhancing the groundwater recharge during the summer monsoon seasons are needed to ensure future agricultural production.

A diagnostic approach to modeling watersheds with human interference

Most watersheds have human impacts that modify hydrological responses differently over a range of timescales. However, these impacts are not accounted for in most hydrological models. Human impacts in watersheds are diverse and case specific, unlike natural hydrologic processes. Incorporating all plausible human impacts comes at a high data acquisition and modeling cost. This raises the question, which human impacts do we need to incorporate to represent observed streamflow patterns at different timescales? To answer this question, we develop a diagnostic approach to modeling watersheds with human interference. This mixed methods approach is informed by the case history and builds on the top-down hydrological modeling approach where process complexity is incrementally added with changing timescales to identify and respond to changing dominant hydrological processes in a given watershed. Here we implement this modeling approach in the East Fork watershed in California, USA for which data on changes in water imports, withdrawals, irrigation and agriculture land cover is available from the early 1940′s, making it an ideal demonstration case. In the East Fork watershed, we find that incorporation of water imports and rights are sufficient to replicate annual patterns of runoff variability, and that adding crop water demand and irrigation enables replication of monthly and daily patterns, while incorporation of groundwater pumping results in negligible improvements. To demonstrate the capabilities of the diagnostic approach in and beyond this case we conducted two computational experiments: checking for needed model structural change and exploring a counterfactual scenario of intensified agriculture.

Groundwater level fluctuation caused by tide and groundwater pumping in coastal multi-layer aquifer system

This paper considered the groundwater head fluctuation induced by tide and pumping in the coastal multi-layered aquifer system. The multi-layered aquifer system comprises an unconfined aquifer, an upper confined aquifer, and a lower confined aquifer. An aquiclude exists between each two aquifers. All the layers terminate at the coastline. The new analytical solutions describing groundwater head variation in the coastal multi-confined aquifer system are derived. Superposition principle and image methods are used for the derivation of the analytical solutions. Analytical solutions of different situations of without considering pumping, of without considering tidal effect, and of N-layered confined aquifers are also derived. The impacts of the parameters of the initial phase shift of tide, pumping rate, position of the pumping well, storage coefficient, and transmissivity on the groundwater head fluctuation are discussed. The analytical solutions are applied with application examples in fitting field observations and parameter estimations. The estimated values of the hydraulic conductivities in the upper and lower confined aquifers are within the range of the values obtained from the field experiments. The fitted results of the analytical solutions capture the main characteristics of groundwater head fluctuation affected by the tide and groundwater pumping. The study of groundwater head fluctuation in the coastal zone is helpful to understand the mechanism of seawater intrusion under the influence of tide and groundwater pumping.

Investigating the impact of irrigation practices on hydrologic fluxes in a highly managed river basin

Irrigation practices and sources can have significant impacts on water resources and the hydrologic fluxes that control these resources. To better manage water resources and future water supply, the influence of irrigation practices and management on these hydrologic fluxes should be quantified in time and space at varying scales, under potential irrigation management practices. To fulfill this objective, a surface-subsurface modeling approach was applied to simulate watershed-scale hydrologic processes in the Cache la Poudre River Basin, Colorado, USA (4824 km2), in which both surface water irrigation and groundwater irrigation are prevalent. The model chosen for this study is the watershed model SWAT+, using the spatially distributed, physically based groundwater module gwflow, in which unconfined groundwater storage, flows, and interaction with land surface features are simulated using a collection of grid cells that represent control volumes of the aquifer. Major groundwater inflows and outflows include pumping, recharge, groundwater-channel exchange, groundwater-lake exchange, and tile drainage outflow. To investigate the impact of irrigation practices, detailed surface and groundwater irrigation routines and canal-aquifer interactions were added to the SWAT+ source code, requiring information of irrigation sources and irrigation canal locations throughout the river basin. Model calibration and testing was performed using monthly stream discharge and groundwater head. The calibrated model is used to quantify the impact of surface water and groundwater irrigation scenarios on water availability and hydrologic fluxes within the river basin. A total of 22 scenarios were conducted and grouped into five main groups: irrigation source, irrigation amount, irrigation type, canal bed thickness, and partial or full sealing of earthen irrigation canals. Using groundwater as the only irrigation source decreases groundwater discharge to streams (by 14 %) due to lowering groundwater levels; converting flood irrigation to sprinkler irrigation throughout the basin decreases surface runoff by 22 %; and sealing earthen canals leads to a lowering of groundwater levels, which decreases groundwater discharge to streams by 9 %, leading to an overall decrease in streamflow in the Cache la Poudre River and changes to temporal patterns in streamflow. Overall, irrigation amount and type and canal sealing have a small impact on total groundwater storage, compared to changes in the percent of fields irrigated by groundwater pumping. Results are helpful for informed decision-making in agriculture water management and can lead to sustainable, efficient, and equitable use of water resources, helping to address the challenges posed by water scarcity and environmental conservation.

Modeling the Impact of Groundwater Pumping on Karst Geotechnical Risks in Sete Lagoas (MG), Brazil

Modeling the Impact of Groundwater Pumping on Karst Geotechnical Risks in Sete Lagoas (MG), Brazil

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.

Assessing sustainable development pathways for water, food, and energy security in a transboundary river basin

Worldwide hundreds of millions of people suffer from water, food and energy insecurity in transboundary river basins, such as the Zambezi River Basin. The interconnected nature of nexus is often not recognized in investment planning and many regional policymakers lack adequate tools to tackle it. Future growing demands and climate change add an additional challenge. In this study, we combine policy relevant co-developed stakeholder scenarios and integrated nexus modeling tools to identify key solutions to achieve sustainable development in the Zambezi. Results show that siloed development without coordination achieves the least economic and social benefits in the long term. Prioritizing economic benefits by maximizing the use of available natural resources results in the expansion of irrigated areas by more than a million hectares and increase in hydropower production by 22,000 GWh/year in the coming decades, bringing significant economic benefits, up to $12.7 billion per year, but causes local water scarcity and negative impacts on the environment. Combining environmental protection policies with sustainable investments of $7.2 billion per year (e.g. groundwater pumping and wastewater treatment and reuse, irrigation efficiency improvements, and farmer support aimed to improve food security and productivity) results in significantly higher social benefits with economic benefits that still reach $11.7 billion per year.

Semi-Analytical Modeling of Transient Stream Drawdown and Depletion in Response to Aquifer Pumping.

Analytical and semi-analytical models for stream depletion with transient stream stage drawdown induced by groundwater pumping are developed to address a deficiency in existing models, namely, the use of a fixed stream stage condition at the stream-aquifer interface. Field data are presented to demonstrate that stream stage drawdown does indeed occur in response to groundwater pumping near aquifer-connected streams. A model that predicts stream depletion with transient stream drawdown is developed based on stream channel mass conservation and finite stream channel storage. The resulting models are shown to reduce to existing fixed-stage models in the limit as stream channel storage becomes infinitely large, and to the confined aquifer flow with a no-flow boundary at the streambed in the limit as stream storage becomes vanishingly small. The model is applied to field measurements of aquifer and stream drawdown, giving estimates of aquifer hydraulic parameters, streambed conductance, and a measure of stream channel storage. The results of the modeling and data analysis presented herein have implications for sustainable groundwater management.

Mapping and assessment of groundwater pollution risks in the main aquifer of the Mostaganem plateau (Northwest Algeria): utilizing the novel vulnerability index and decision tree model.

Water plays a pivotal role in socio-economic development in Algeria. However, the overexploitations of groundwater resources, water scarcity, and the proliferation of pollution sources (including industrial and urban effluents, untreated landfills, and chemical fertilizers, etc.) have resulted in substantial groundwater contamination. Preserving water irrigation quality has thus become a primary priority, capturing the attention of both scientists and local authorities. The current study introduces an innovative method to mapping contamination risks, integrating vulnerability assessments, land use patterns (as a sources of pollution), and groundwater overexploitation (represented by the waterhole density) through the implementation of a decision tree model. The resulting risk map illustrates the probability of contamination occurrence in the substantial aquifer on the plateau of Mostaganem. An agricultural region characterized by the intensive nutrients and pesticides use, the significant presence of septic tanks, widespread illegal dumping, and a technical landfill not compliant with environmental standards. The critical situation in the region is exacerbated by excessive groundwater pumping surpassing the aquifer's natural replenishment capacity (with 115 boreholes and 6345 operational wells), especially in a semi-arid climate featuring limited water resources and frequent drought. Vulnerability was evaluated using the DRFTID method, a derivative of the DRASTIC model, considering parameters such as depth to groundwater, recharge, fracture density, slope, nature of the unsaturated zone, and the drainage density. All these parameters are combined with analyses of inter-parameter relationship effects. The results show a spatial distribution into three risk levels (low, medium, and high), with 31.5% designated as high risk, and 56% as medium risk. The validation of this mapping relies on the assessment of physicochemical analyses in samples collected between 2010 and 2020. The results indicate elevated groundwater contamination levels in samples. Chloride exceeded acceptable levels by 100%, nitrate by 71%, calcium by 50%, and sodium by 42%. These elevated concentrations impact electrical conductivity, resulting in highly mineralized water attributed to anthropogenic agricultural pollution and septic tank discharges. High-risk zones align with areas exhibiting elevated nitrate and chloride concentrations. This model, deemed satisfactory, significantly enhances the sustainable management of water resources and irrigated land across various areas. In the long term, it would be beneficial to refine "vulnerability and risk" models by integrating detailed data on land use, groundwater exploitation, and hydrogeological and hydrochemical characteristics. This approach could improve vulnerability accuracy and pollution risk maps, particularly through detailed local data availability. It is also crucial that public authorities support these initiatives by adapting them to local geographical and climatic specificities on a regional and national scale. Finally, these studies have the potential to foster sustainable development at different geographical levels.

An approach for the design of dewatering systems: the case of an excavation for the construction of the assembly shaft of a tunnel boring machine

Robust approaches are needed for designing efficient dewatering systems of deep excavations below the water table to avoid unforeseen incidents (e.g., bottom instabilities in deep excavations and flooding, among others). This paper proposes a methodology, which integrates existing experiences, that was adopted to design the dewatering system of an excavation in the city of Barcelona (Spain). The approach consists of combining: (i) detailed geological and hydrogeological characterizations, (ii) numerical modelling for parameter estimation and drawdown predictions, and (iii) analytical assessment for stability evaluation and soil deformation predictions. The idea is that by combining a set of relatively easy to apply methods, it is possible to successfully solve a complex and risky problem. The methodology allows designing efficient dewatering systems, increasing safety and mitigating potential impacts of groundwater pumping. The most significant conclusion is that the most important step of the proposed approach is the hydrogeological characterization because it allows building realistic and representative numerical models to address most of the challenges associated to dewatering.

Assessment of spatio-temporal variations in groundwater quality for the groundwater-dependent Maltese islands

Study regionMaltese islands Study focusThe Maltese islands are situated in the Mediterranean Sea, characterized by a semi-arid climate, and encounter increased levels of water stress. This study conducted a hydrochemical analysis of 35 groundwater samples to evaluate the suitability of the current groundwater for agricultural and domestic purposes. Additionally, three-dimensional numerical modeling was conducted to estimate long-term changes in groundwater levels and saline water distributions over 30 years, under the assumption that groundwater pumping will persist at the current rate. New hydrological insights for the regionSalinity factors that classify groundwater in this region can potentially be used for the irrigation of salt-tolerant crops. The output of the modeling calculations suggests that groundwater levels were expected to decrease significantly across most of the island, particularly around gallery areas. Descending the water table may compromise the discharge of coastal groundwater and potentially accelerate seawater intrusion into the inner island areas. Hydrochemical calculations indicated that an increase in salinity induced variations in saturation conditions, leading to a decrease in calcite and an increase in anhydrite, dolomite, and gypsum. The water quality characteristics and contamination evaluations conducted in this study are valuable for the development of long-term alternatives for water resource conservation in this region.

Potential impacts of saline groundwater pumping on seawater intrusion in a coastal aquifer system

ABSTRACT Desalination plants employing feed water sourced from saline groundwater (SGW) are a feasible approach to tackle freshwater scarcity and seawater intrusion (SWI). Available studies lacked comprehensive analysis quantifying the impact of pumping from a coastal aquifer, on changes in solute transport mechanism. This study investigates the impact of different rates of SGW pumping on the solute transport in a coastal aquifer. A regional-scale model resembling the Upper Floridan aquifer was modelled using SEAWAT to quantify SWI variables. The study found that the length of intrusion of toe (Ltoe), width of mixing zone (WMZ) and residual salt mass (RSM) varied with dispersivity values. The ratio of saltwater to freshwater influx was unaffected by dispersivity values. Significant decrease in the toe-length occurred when the pumping rate was highest and the dispersivity was lowest. The WMZ was found to be the most sensitive SWI variable towards varying dispersivity, with 65% difference for higher pumping rates. The mid-bottom region was experiencing substantial modifications, leading to an inclined response at increased pumping rates, which suggested that the diluting process was primarily taking place in the bottom portion. This study gives insight into saline wedge movement in a coastal aquifer system which will benefit in the design of SGW well system for desalination plants.

Study on Zoning Effect of Shallow Geothermal Energy Suitability Based on Structural Matrix Method

Geothermal energy is a clean, renewable resource that can be harnessed to help China achieve its twofold carbon goal and advance its energy security policy. Shallow geothermal, middle-deep geothermal, and dry hot rock geothermal all belong to the clean energy. The thermal energy held in rock, soil, groundwater, and surface water up to a depth of 200 metres is referred to as the shallow geothermal variety, which is characterized by temperatures below 25∘C. Its use is mostly dependent on ground source heat pump technology. The ground source heat pump ground pipe heat exchange system, the ground source heat pump groundwater heat exchange system, and the ground source heat pump surface water heat exchange system are all included in the shallow geothermal heat exchange mechanism. The structural matrix approach is used in this study to determine if the groundwater heat exchange system for the shallow geothermal ground source heat pump in Sanmenxia’s urban setting is appropriate. The results showed that: the most influential factor was hydrogeological conditions, followed by hydrodynamic and water chemistry conditions. Aquifer recharge capacity and water capacity was the necessary condition of suitability partition. Studied hydrodynamic field and chemical field, analyzed aquifer thickness and groundwater flow under current conditions and determined the appropriate zoning, proposed groundwater aquifers and recharge horizon.

Reversibility of seawater intrusion in a coastal aquifer: Insights from long-term field observation and numerical modeling

It is essential to understand basis processes affecting the reversibility of seawater intrusion (SWI) and the related timescale after groundwater pumping stopped for coastal groundwater management. Groundwater salinity variations presented by previous studies showed a fast SWI process and the following seawater retreat (SWR) process indicated by overall salinity decrease in the coast karst aquifer in the Dalian Peninsula, northeast China. Cross-sectional variable-density flow and transport simulations using equivalent porous medium (EPM) model, dual-domain (DDM) model and the EPM with a single discrete feature representative of conduit flow (EPM-DF) are conducted to understand the SWI reversibility related to the characteristics of the flow system, including aquifer parameters and seaside boundary conditions. Large dispersity combined with a low salinity concentration at the sea boundary are necessary in the EPM and DDM models to produce a fast SWI and low salinity concentration as observed. The enhanced dispersion in the DDM model enhances the mixing in the transition zone (TZ) and produces more obvious seasonal variation but longer SWR process compared to the EPM model. The EPM-DF model produces significant salinity seasonal variation during the SWI process and a fast decrease in the SWR process. The overall fast system response but low peak concentration during the SWI might be attributed to the highly heterogeneous characteristics of the karst aquifer system, which produces a wide front edge of TZ as observed. The dispersion-dominated EPM and DDM models produced higher degree of SWI reversibility compared to the EPM-DF model, as indicated by the weaker lag effects between groundwater levels and salinity concentration. Moreover, the SWI reversibility may arise not only from the heterogeneous characteristics of the karstic aquifer system but also from the rate for rise in the inland groundwater level during the seasonal variation cycle. An overall SWR process can be divided into two stages: the first stage with rapid decrease in salinity concentration but small changes in toe associated with TZ widening and the second stage with rapid toe retreat during aquifer flushing. The flushing of the brine leakage from the solar salt field may extend the SWR process. Considering this relatively longer water quality response time than the time span in general groundwater management plans, a reasonable objective and how maintain the hydraulic head during the SWI controlling have been of a great concern to the coastal groundwater management.

The cost of mismanaging crop heat stress with irrigation: Evidence from the mid-south USA

Field level data from a voluntary water use reporting program in the Delta region of Mississippi (MS), USA, provides empirical evidence that crop growers increase the amount of groundwater pumped for irrigation during periods of high temperature (degree days above 32 C). Regression analysis reveals that growers apply excess irrigation to cope with high temperature conditions while growing season evapotranspiration and precipitation are not significant factors in their decision of how much irrigation to apply. The existing literature indicates that excess water does not alleviate the harmful effect of extreme heat, making the excess irrigation wasteful and costly. Additional degree days above 32 C are associated with a 4.6 mm increase in irrigation depth (46 m3ha−1). This result may be partially explained by the fact that most farmers use visual cues (such as leaf folding which correlate with air temperature) to initiate irrigation events regardless of soil moisture contents. To quantify the impact of this mismatch, we estimate that shifting the underlying sensitivity in the farmers’ minds by 1 C would reduce groundwater pumpage by 800862 mega liters across the Delta region of Mississippi, USA. The monetary cost of mismanaging heat stress with excessive irrigation is estimated at a minimum of over US$33 million per year. We further identify two additional possible distortions affecting the demand for irrigation groundwater: (i) overestimated benefits from irrigation; and (ii) underestimated groundwater pumping cost. The policy implication is that more efforts and incentives should be placed for programs that affect the producers’ water management mindset, such as "Master Irrigator" programs that will reduce or eliminate the identified groundwater distortions and optimize benefits from irrigation.

Hydrogeologic Framework Model‐Based Numerical Simulation of Groundwater Flow and Salt Transport and Analytic Hierarchy Process‐Based Multi‐Criteria Evaluation of Optimal Pumping Location and Rate for Mitigation of Seawater Intrusion in a Complex Coastal Aquifer System

AbstractA series of hydrogeologic framework model (HFM)‐based steady‐ and transient‐state numerical simulations is performed first using a coupled subsurface flow‐transport numerical model to analyze groundwater flow and salt transport in an actual three‐dimensional complex coastal aquifer system before and during groundwater pumping. A series of analytic hierarchy process (AHP)‐based multi‐criteria evaluations is then performed applying a multi‐criteria decision‐making approach to determine optimal pumping location and rate for a new pumping well in the complex coastal aquifer system during groundwater pumping. The complex coastal aquifer system is composed of six anisotropic fractured porous geologic media (five rock formations and one fault) and three isotropic porous geologic media (three soil formations) and shows high geometric irregularity and significant heterogeneity and anisotropy of the nine geologic media. Results of the steady‐state numerical simulations show successful model calibration with 26 measured groundwater levels and two observed seawater intrusion front lines. The latter two are determined by spatial interpolation and extrapolation of electrical conductivity logging data and electrical resistivity survey data, respectively. Based on the status and prospect of necessary water uses and available groundwater resources, the field observations of groundwater and seawater intrusion, and the analyses of the steady‐state numerical simulation after the model calibration, six candidate pumping locations are selected for the new pumping well. In addition, from six preliminary individual transient‐state numerical simulations, maximum pumping rates at the six candidate pumping locations are calculated first, and a set of six incremental candidate pumping rates is then assigned at each of the six candidate pumping locations. Results of the transients‐state numerical simulations show that groundwater flow and salt transport are spatially and temporally changed, and seawater intrusion is further intensified by groundwater pumping. In addition, the magnitudes of such spatial and temporal changes and intensification are significantly different depending on the candidate pumping locations and rates. Results of the steady‐ and transient‐state numerical simulations also show that both complexity (geometric irregularity, heterogeneity, and anisotropy including the fault) and topography have significant effects on the spatial distributions and temporal changes of groundwater flow and salt transport in the coastal aquifer system before and during groundwater pumping. In addition, results of statistical estimations of the mesh Peclet and Courant numbers confirm acceptabilities of minimizing numerical dispersion in the steady‐ and transient‐state numerical simulations. Based on the analyses of the transient‐state numerical simulations, eight multiple criteria are chosen to judge, prioritize, and rank the six candidate pumping locations and six candidate pumping rates for optimal pumping. Results of the multi‐criteria evaluations determine the optimal pumping location and rate for the new pumping well among the six candidate pumping locations and six candidate pumping rates. In addition, results of consistency checks confirm consistencies of judgments in the multi‐criteria evaluations.

Analysis of Groundwater Time Series With Limited Pumping Information in Unconfined Aquifer: Response Function Based on Lagging Theory

AbstractGroundwater extraction from aquifers is a common practice for human use, and variations in groundwater levels can provide valuable information on the hydrogeological properties of the aquifer. However, reliable data on pumping rates and distribution are often lacking due to unsupervised groundwater pumping activities. This study presents a new mathematical model for transfer function modeling that depicts the drawdown response caused by pumping in an unconfined aquifer system. To account for the dense and unsupervised pumping events, the uniform pumping approach was used to estimate these effects. To more accurately represent unconfined flow, the model first integrates lagging theory into a response function derived from the Boussinesq equation. The lagging theory accounts for the effects of both inertial force and capillary suction. Furthermore, the model has been used to derive both specific yield and transmissivity along with two lagging parameters simultaneously using only groundwater level information from the Choshui River region in Taiwan. The estimated results suggest that this approach provides reliable estimates of hydrogeological parameters, demonstrating its usefulness for water resource management and water budget evaluation.