Groundwater Pumping Research Articles

Understanding the phenomenon of saltwater intrusion sourced from desalination plants at coastal aquifers.

Members of the Gulf Cooperation Council countries Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates rely on desalination to produce water for domestic use. Desalination produces brine that may intrude into the aquifers to pollute the fresh groundwater because of the concentration gradient and groundwater pumping. Modeling the trends of saltwater intrusion needs theoretical understanding and thorough logical experimentation. The objective of this exercise was to understand the phenomenon of saltwater intrusion using an existing set of data analyzed with the convective-diffusion equation and the two-region mobile-immobile solution model. The objective was achieved by optimizing non-measurable solute transport parameters from an existing set of data generated from a series of logical miscible displacements of potassium bromide through sepiolite minerals and curve-fitting simulations. Assumptions included that solute displacements through sepiolite porous media and the related simulations represented the phenomenon of saltwater intrusion under non-equilibrium conditions of porous media mimicking the aquifers. Miscible displacements of potassium bromide were observed from a column of 2.0-2.8mm aggregates of sepiolite over 4 ranges of concentration and at 11 displacement speeds under saturated vertical flow deionized water and vice versa. Breakthrough curves of both bromide and potassium ions were analyzed by a curve-fitting technique to optimize transport parameters assuming solute movement was governed (i) by the convective-diffusion equation and (ii) the two-region mobile-immobile solution model. Column Peclet numbers from the two analyses were identical for potassium ions but those for bromide ions were c. 60% greater from the two-region model than from the convective-diffusion equation. For the two-region model, dispersion coefficients were well defined and remained unchanged from the convective-diffusion equation for potassium ions but decreased for bromide ions. Retardation factors for bromide ions were approximately the same, but those for potassium ions, though > 1, were poorly defined. In order to design mitigation strategies for avoiding groundwater contamination, this study's findings may help model groundwater pollution caused by the activities of desalination of seawater, which produces concentrated liquid that intrudes into the coastal aquifer through miscible displacement. However, robust saltwater intrusion models may be considered in future studies to confirm the results of the approach presented in this exercise. Field data on the groundwater contamination levels may be collected to compare with simulated trends drawn from the saltwater intrusion models and the curve-fitting technique used in this work. A comparison of the output from the two types of models may help determine the right option to understand the phenomena of saltwater intrusion into coastal aquifers of various characteristics.

Estimation of Streamflow Depletion Caused by Groundwater Withdrawal in the Bokhacheon Watershed in South Korea Using the Modified SWAT Model

Understanding the effects of groundwater withdrawal on streamflow depletion is important for effectively managing water resources. The Soil and Water Assessment Tool (SWAT) model has a groundwater module to calculate the groundwater budget and groundwater discharge. However, the water pumped from the aquifer is not considered in the SWAT module that estimates groundwater discharge. Therefore, this module was modified to consider the impact of groundwater pumping on the changes in groundwater discharge in the Bokhacheon watershed, South Korea. The model’s water transfer module was improved to allow water from the aquifer to be transferred to destination locations, such as residential, industrial, and agricultural lands. Using the modified SWAT, streamflow responses to groundwater extraction were simulated for 2011–2019. The groundwater withdrawal induced decreases of 14.6 and 24.2% in low and drought flows, respectively, at the watershed’s outlet. The groundwater withdrawals decreased groundwater flow and total water yield by 23.5% and 9.8%, respectively, and increased surface flow, lateral flow, percolation, soil water, and evapotranspiration owing to the increased soil moisture resulting from the partial re-infiltration of the groundwater pumped for agricultural irrigation. The modified SWAT can effectively estimate streamflow depletion resulting from groundwater pumping without extensive hydrogeological input data and computational time.

Drilling Deeper in Shallow Geoexchange Heat Pump Systems—Thermogeological, Energy and Hydraulic Benefits and Restraints

In the last decade, due to climate change concerns and new environmental regulations in the EU, there was a tremendous rise in installed heat pump systems in new homes and buildings. The majority of these installed units are related to air-source heat pumps, as they offer a good trade-off between capital and operating expenses. However, when analysing heating and cooling heat pump systems from the primary energy consumption and ecological aspects, groundwater and shallow geothermal heat pump systems offer superior efficiency, compared to all market-available thermo-technical systems today. In the last decade, ground-source systems have seen some technological improvement by employing new borehole heat exchanger designs, such as piping with internal fins and a wider diameter (so called Turbocollector) to enhance the heat transfer between fluid and rock, as well as to reduce the pressure drop in the system. Furthermore, the process of drilling deeper offers higher ground temperatures and consequently higher seasonal performance factors in the heating cycle, due to the effect of the geothermal gradient. Nevertheless, although deeper boreholes provide better heat extraction rates per meter during the heat pump heating cycle, at the same time, it reduces heat rejection rates during the heat pump cooling cycle. The objective of this paper is to analyse and evaluate benefits and downsides of a new approach in the heat pump system design with deeper borehole heat exchangers of up to 300 m, comparing it to the traditional design of double-loop exchangers with 100 m depth. The geothermal borehole grid design simulation model, along with heat extraction and rejection, is performed on a yearly basis. The results are showing that the benefits of shallow geothermal boreholes, from the hydraulic and thermodynamic point of view, still dominate over deeper solutions.

Identifying robust adaptive irrigation operating policies to balance deeply uncertain economic food production and groundwater sustainability trade-offs

Increasing irrigation demand has heavily relied on groundwater use, especially in places with highly variable water supplies that are vulnerable to drought. Groundwater management in agriculture is becoming increasingly challenging given the growing effects from overdraft and groundwater depletion worldwide. However, multiple challenges emerge when seeking to develop sustainable groundwater management in irrigated systems, such as trade-offs between the economic revenues from food production and groundwater resources, as well as the broad array of uncertainties in food–water systems. In this study we explore the applicability of Evolutionary Multi-Objective Direct Policy Search (EMODPS) to identify adaptive irrigation policies that water agencies and farmers can implement including operational decisions related to land use and groundwater use controls as well as groundwater pumping fees. The EMODPS framework yields state-aware, adaptive policies that respond dynamically as system state conditions change, for example with variable surface water (e.g., shifting management strategies across wet versus dry years). For this study, we focus on the Semitropic Water Storage district located in the San Joaquin Valley, California to provide broader insights relevant to ongoing efforts to improve groundwater sustainability in the state. Our findings demonstrate that adaptive irrigation policies can achieve sufficiently flexible groundwater management to acceptably balance revenue and sustainability goals across a wide range of uncertain future scenarios. Among the evaluated policy decisions, pumping restrictions and reductions in inflexible irrigation demands from tree crops are actions that can support dry-year pumping while maximizing groundwater storage recovery during wet years. Policies suggest that an adaptive pumping fee is the most flexible decision to control groundwater pumping and land use.

Sustainable groundwater management and its implications for agricultural land repurposing

In this paper, we examine the implications of groundwater sustainability policies on agricultural land retirement and how retired land can be repurposed to minimize social, economic, and environmental harms, while maximizing potential benefits. Globally, as water resources are strained by increasing agricultural demand and biophysical factors, policies are enacted to restrict groundwater pumping for irrigated agriculture in order to stem social, economic, and environmental harm. However, little is known about the implications of land retirement on ecosystems and people, and how this land can be best repurposed. Using Kern County, CA, as a case study, we draw from 23 qualitative interviews with stakeholders in the agricultural, water, and conservation sectors to understand the impacts of sustainable groundwater management policy and options for land repurposing. Stakeholders in our study outlined both positive and negative impacts of such policies across the region, including increased financial costs of agricultural production, crop type switches to perennial crops such as trees and vines, and improved communication and collaboration among stakeholders. Stakeholders discussed options for land repurposing to maximize ecological, social, and economic benefits, including habitat restoration, installation of solar farms, grazing, groundwater recharge, temporary fallowing, and recreation and parks. Finally, we propose recommendations to maximize the benefits and minimize the harms from the retirement and repurposing of agricultural land: (1) increasing regional planning and cross-stakeholder communication for strategic land repurposing, (2) minimizing the burden of policies that may restrict land repurposing options, and (3) ensuring financial incentives exist for landowners to repurpose their land.

Assessing Artificial Recharge on Groundwater Quantity Using Wells Recharge

In arid and semi-arid countries like Iraq, which suffer from water scarcity due to the effects of climate change and decreased surface water flow, groundwater is considered a vital source of irrigation water. This study is concerned with the influence of artificial recharge on the rehabilitation of the unconfined aquifer called Al-Dibdibba, located between the cities of Najaf and Kerbala in central Iraq around 31°550′ N and 32°450′ N and 43°300′ E and 44°300′ E. Due to excessive groundwater pumping rates for irrigation, this aquifer has suffered from groundwater decline and increased salinization during the previous 20 years. By establishing a conceptual model in the groundwater modeling system software (GMS), a numerical model was made to simulate groundwater flow. Artificial recharge using recycled water (tertiary treatment) from Kerbala's primary WWTP was carried out using 25 injection wells. The model was calibrated against historical and observed water level data for periods from 2016 to 2017. Three scenarios to predict how the aquifer would act with artificial recharge of 5%, 8%, and 10% from the total daily outflow of the WWTP in Kerbala (100000 m3/day) were studied. The calibration model met the observed values of groundwater levels with R2 = 0.989 for steady-state simulations and R2 = 0.987 for transient simulations. In the final analysis of the simulation, the results show that the maximum predicted groundwater level was raised by the injection of treated water through 25 wells by 1.05 m for 5000 m3/day, 2 m for 8000 m3/day, and 3 m for 10,000 m3/day recharge pumping rates. In addition, if water were pumped into the aquifer, it might support the development of agricultural lands covering more than 93 km2. So, artificial recharge can be considered one of the important solutions to adaptation to the effects of climate change and desertification in Iraq. Doi: 10.28991/CEJ-2023-09-09-010 Full Text: PDF

Estimating the Maximum Safe Pumping Rate in Sloping Unconfined Coastal Aquifers

AbstractUnconfined coastal aquifers with a sloping aquifer bed are ubiquitous. However, most analytical solutions previously developed to estimate pumping‐induced seawater intrusion considered a horizontal aquifer bed. In this study, we first developed a steady‐state analytical solution to quantify the maximum safe pumping rate in sloping unconfined coastal aquifers with a fixed‐flux inland boundary condition, using the single potential approach. The analytical solution corrected by an empirical factor is validated against the numerical simulation, which reproduces the corresponding numerical results well. It is found that coastal aquifers with a higher aquifer bed toward inland (i.e., a positive sloping angle) yield a higher maximum safe pumping rate than that of coastal aquifers with a horizontal aquifer base, since the elevated freshwater head prevents seawater intrusion and enhances groundwater pumping. Specifically, for the aquifer bases with the sloping angle of 0.01 and −0.01, the maximum safe pumping rate is increased by 42.6% and decreased by 48.4%, respectively, in comparison to the case of a horizontal aquifer base, suggesting that neglecting the aquifer base slop can result in a significant error in estimating the maximum safe pumping rate. Moreover, the sensitivity analysis reveals that the maximum safe pumping rate increases with a lower hydraulic conductivity and a larger dispersivity. Our results provide valuable insights into the effect of the aquifer base slope on the maximum safe pumping in coastal aquifers, and analytical solutions developed can serve as a powerful tool for quick assessment of pumping‐induced seawater intrusion in sloping unconfined coastal aquifers.

Large‐Scale Groundwater Monitoring in Brazil Assisted With Satellite‐Based Artificial Intelligence Techniques

AbstractHere, we develop and test an artificial intelligence (AI)‐based approach to monitor major Brazilian aquifers. The approach combines Gravity Recovery and Climate Experiment (GRACE) data and ground‐based hydrogeological measurements from Brazil's Integrated Groundwater Monitoring Network at hundreds of wells distributed in 12 aquifers across the country. We tested model ensembles based on three AI approaches: Extreme Gradient Boost, Light Gradient Boosting Model and CatBoost, followed by a Linear Regression step. The approach is further boosted with wavelet and seasonal decomposition processes applied to GRACE data. To determine the AI‐based model's sensitivity to data availability, we propose four experiments combining hydrogeological measurements from different aquifers. Groundwater storage (GWS) estimates from the Global Land Data Assimilation System (GLDAS) are used as benchmark. A sensitivity analysis shows that the LR‐based model ensemble is the best suited and to reproduce GWS change in all studied Brazilian aquifers. Results show that the proposed approach outperforms GLDAS in all experiments, with an root mean square error (RMSE) value of 2.68 cm for the experiment that covers all monitored wells in Brazil. GLDAS resulted in RMSE = 6.76 cm. Using our AI model outputs, we quantified the GWS change of two major aquifers, Urucuia and Bauru‐Caiuá, over the past two decades: −31 and −6 km3, respectively. Water loss is driven by a prolonged drought across most of the country and intensification of groundwater pumping for irrigation. This study demonstrates that combining satellite data and AI can be a cost‐effective alternative to monitor poorly equipped aquifers at the continental scale, with possible global replicability.

Impacts of Groundwater Pumping for Hydraulic Fracturing on Aquifers Overlying the Eagle Ford Shale.

Hydraulic fracturing (HF) events consume high volumes of water over a short time. When groundwater is the source, the additional pumping by rig/frack supply wells (RFSWs) may impose costs on owners of other sector wells (OSWs) by lowering the hydraulic head. The Carrizo-Wilcox aquifer in south Texas is the main source of water for HF of the Eagle Ford Shale (EFS) Play. The objectives are to assess the impacts of groundwater pumping for HF supply on: (1) hydraulic heads in OSWs located nearby an RFSW and (2) volumetric fluxes between layers of the regional aquifer system compared to a baseline model without the effect of RFSW pumping. The study area spans the footprint of the EFS Play in Texas and extends from 2011 to 2020. The pumping schedules of 2500 RFSWs were estimated from reported pumped water volumes to supply 22,500 HF events. Median annual drawdowns in OSWs ranged from 0.2 to 6.6 m, whereas 95th percentile annual drawdowns exceeded 20 m. The magnitudes of drawdown increased from 2011 to 2020. Of the four layers that comprise the Carrizo-Wilcox aquifer, the upper Wilcox was the most intensively pumped for HF supply. During the peak HF year of 2014, the net flux to the upper Wilcox was 292 Mm3 compared to the baseline net flux for the same year of 278 Mm3-a relative gain of 14 Mm3. Pumping for HF supply has the potential to negatively impact nearby OSWs by capturing water from adjacent aquifer layers.

Irrigation benefits outweigh costs in more US croplands by mid-century

Irrigation can increase crop yields and could be a key climate adaptation strategy. However, future water availability is uncertain. Here we explore the economic costs and benefits of existing and expanded irrigation of maize and soybean throughout the United States. We examine both middle and end of the 21st-century conditions under future climates that span the range of projections. By mid-century we find an expansion in the area where the benefits of irrigation outweigh groundwater pumping and equipment ownership costs. Increased crop water demands limit the region where maize could be sustainably irrigated, but sustainably irrigated soybean is likely feasible throughout regions of the midwestern and southeastern United States. Shifting incentives for installing and maintaining irrigation equipment could place additional challenges on resource availability. It will be important for decision makers to understand and account for local water demand and availability when developing policies guiding irrigation installation and use.

Spatial and seasonal controls on dissolved organic matter composition in shallow aquifers under the rapidly developing city of Patna, India

The distribution and composition of dissolved organic matter (DOM) affects numerous (bio)geochemical processes in environmental matrices including groundwater. This study reports the spatial and seasonal controls on the distribution of groundwater DOM under the rapidly developing city of Patna, Bihar (India). Major DOM constituents were determined from river and groundwater samples taken in both pre- and post-monsoon seasons in 2019, using excitation-emission matrix (EEM) fluorescence spectroscopy. We compared aqueous fluorescent DOM (fDOM) composition to satellite-derived land use data across the field area, testing the hypothesis that the composition of groundwater DOM, and particularly the components associated with surface-derived ingress, may be controlled, in part, by land use. In the pre-monsoon season, the prominence of tryptophan-like components likely generated from recent biological activity overwhelmed the humic-like and tyrosine-like fluorescence signals. Evidence from fluorescence data suggest groundwater in the post-monsoon season is composed of predominantly i) plant-derived matter and ii) anthropogenically influenced DOM (e.g. tryptophan-like components). Organic tracers, as well as Eh and Cl−, suggest monsoonal events mobilise surface-derived material from the unsaturated zone, causing dissolved organic carbon (DOC) of more microbial nature to infiltrate to >100 m depth. A correlation between higher protein:humic-like fluorescence and lower vegetation index (NDVI), determined from satellite-based land use data, in the post-monsoon season, indicates the ingression of wastewater-derived OM in groundwater under the urban area. Attenuated protein:humic-like fluorescence in groundwater close to the river points towards the mixing of groundwater and river water. This ingress of surface-derived OM is plausibly exacerbated by intensive groundwater pumping under these areas. Our approach to link the composition of aqueous organics with land use could easily be adapted for similar hydrogeochemical settings to determine the factors controlling groundwater DOM composition in various contexts.

Geospatial model for allocating favorable plots for groundwater-dependent cultivation activities in Egypt

Moving towards horizontal expansion in the vast barren lands to alleviate overpopulation along the Nile River is imperative to Egypt’s 2030 sustainable development strategy. Accordingly, a mega reclamation project was advocated with a key goal of achieving food self-sufficiency. Solar-powered groundwater pumping system was adopted as the main water supply. Planning efforts are therefore inevitable to help locate the most favourable sites for such extensive cultivation activities. Herein, a multicriteria decision analysis was conducted to facilitate the zoning of potential rural communities across the northern portions of the Western Desert of Egypt. For this purpose, data of groundwater exploration, soil characterization, terrestrial accessibility, insolation intensity, and terrain information were fused to produce a high-resolution suitability map. The analytical hierarchy process approach was adopted to set the weighted importance of adopted criteria. The study area was categorized into Best, Good, Moderate, Fair, Poor, and Restricted classes at 1.7%, 13%, 42.6%, 26%, 10%, and 3%, respectively, of the entire region, while the constrained plots were masked out. The implemented and proposed wells fields within the underway national rural development project extend over agriculturally suitable pixels affirming the validity of the developed geospatial model. About 1.5 million ha, representing 7.2% of the undeveloped area, were found to be highly suitable for future expansion of agribusiness activities. The generated priority map will assist the decision-makers in the planning procedures for ongoing reclamation activities throughout Egypt.

Ramifications of groundwater model in WRF/Noah‐MP coupled system: Effects on soil‐moisture and regional climate simulation

AbstractSoil moisture is a key variable that contributes for flux partitioning into sensible and latent heat components. There is a pressing need to study the impacts of shallow groundwater table dynamics on antecedent soil moisture and corresponding feedbacks to atmosphere. In this study, we evaluate WRF‐NoahMP simulated soil moisture using two experimental configurations: one with the default, free drainage approach (CTL) and with Miguez‐Macho groundwater scheme (GW). Results are presented for the study conducted over Ganga River basin, India between the years 2008 and 2014 for all the three seasons (pre‐monsoon, monsoon, post‐monsoon). It was observed that the GW model runs, improve soil moisture in topmost and bottom‐most layers. We discovered that the simulations improved temporal negative bias of seasonal accumulation during monsoon by around 91 mm. In addition, the average negative bias in latent heat flux improved by around 28 W/m2. Compared to CTL, GW was found to contribute additional atmospheric moisture content ranging between 3% and 5%. Comparison with in‐situ ground water showed that model overestimates the ground water table depth. This can be attributed to the ability of the model to only simulate natural occurring variabilities and lack of inclusion of anthropogenic factors such as ground water pumping in the model. The groundwater trend in Ganga is declining at alarming rate. In addition, if over exploitation of groundwater is not monitored properly, water and food scarcity is an imminent threat to the country's economy. To the best of authors knowledge, this is the first study of its kind to be implemented over Ganga basin, which evaluates the role of shallow ground water table on regional climate using coupled atmosphere‐land surface‐groundwater model. In summary, we highlight that the groundwater component along with WRF‐NoahMP coupled model improves soil moisture and precipitation representation over the Ganga basin.

Early Warning Indicators of Groundwater Drought in Mountainous Regions

AbstractAquifers in mountainous regions are susceptible to drought. However, the diverse hydroclimatology, the small and responsive aquifers, and the varied nature of interactions between groundwater and surface water lead to complex groundwater level responses that are challenging to interpret for understanding groundwater drought. In this study, generalized additive models (GAMs) are used to explore the sensitivity of summer groundwater levels to various climate and hydrological predictor variables (indicators) in each of a snowmelt‐ and rainfall‐dominated hydroclimatic regime in British Columbia, Canada. A sensitivity analysis explores individual seasonal predictor variables, station versus gridded climate data, teleconnection indices, and time series length. GAMs are then generated for different combinations of predictor variables to identify the best combination for each region. In the snowmelt‐dominated regime, maximum spring temperature, maximum snow water equivalent, and the winter Nino 3.4 index is the best combination of variables for predicting summer groundwater levels. In the rainfall‐dominated regime, maximum spring temperature, winter precipitation, and spring streamflow is the best combination. The unique combinations of predictor variables for each region can be used as early warning indicators for groundwater drought preparedness by water managers prior to the beginning of the summer. The Standardized Groundwater Level Index (SGI) is also effective at indicating which wells had pronounced responses to periods of drought in each region. However, the SGI differed among aquifers of similar type, suggesting other factors such as aquifer response mechanism and groundwater pumping may have an important influence on the SGI.

3D geological modelling of the Bologna urban area (Italy)

Urban geological modelling plays a crucial role in facilitating the sustainable utilization of the urban subsurface and the development of effective strategies for geohazard mitigation. Traditionally, geological models of urban areas rely on lithological correlations of boreholes and well data. However, in complex depositional settings such as alluvial environments, where the standard concepts of superposition and lateral continuity of strata are often violated, lithostratigraphic correlation can be challenging even over short distances, leading to considerable uncertainty in the final geological model. Therefore, in such cases, lithofacies analysis can provide a more robust categorisation of subsurface geological units as lithofacies mainly reflect the depositional process, while their associations provide a reliable picture of sedimentary bodies and their geometries. In this work, we used the lithofacies correlation approach to develop a 3D geological model of the urban area of Bologna (Italy) where a complex, thick alluvial succession makes lithological correlations very difficult. To minimize subjectivity, we re-interpreted 940 existing borehole logs in terms of depositional facies and combined stratigraphic data with geophysical HSVR (Horizontal to Vertical Spectral Ratio) measurements and surface analysis (morphology and river network) based on a DTM (Digital Terrain Model). This led to the detailed reconstruction of the subsurface depositional architecture, forming the basis for the 3D geological model. The model revealed the presence of three distinct depositional domains with different stratigraphic architectures. From west to east: Domain A (Reno River) corresponds to the gravel-dominated fill of a river valley abruptly passing to Domain B (Bologna urban area) that represents a morphological and stratigraphical divide, topographically elevated with respect to the surrounding areas and characterised by fine-grained deposits with frequent paleosols. Lastly, Domain C (Savena River) exhibits the typical alluvial fan pattern, marked by a gentle convex-up surface morphology with gravelly-sandy deposits with a low degree of lateral amalgamation. The geological model effectively explains the distribution of ground subsidence in Bologna since the 1960s, which is attributable to significant groundwater pumping. This is evident from the comparison of the model with both the ground displacement contours resulting from the 1983–1987 topographic levelling campaign and the subsidence rate map derived from the 2006–2011 Radarsat interferometric survey. Subsidence shows strong variations at the domains' boundaries, especially at the limit between Domain A (Reno River) where high values prevail, and Domain B (Bologna city centre) characterised by the lowest values.

Life cycle greenhouse gas emissions for irrigated corn production in the U.S. great plains

Agricultural management practices improve crop yields to satisfy food demand of the growing population. However, these activities can have negative consequences, including the release of greenhouse gas (GHG) emissions that contribute to global climate change. To mitigate this global environmental problem, the management practices that contribute the most to system GHG emissions should be identified and targeted to mitigate emissions. Accordingly, we estimated the cradle-to-product GHG emissions of irrigated corn production under various farmer-selected scenarios at an experimental testing field in the semi-arid U.S. Great Plains. We applied a carbon footprint approach to quantify life cycle GHG emissions associated with pre-field (e.g., energy production, fertilizer production) and in-field (e.g., groundwater pumping, fertilizer application) activities within fourteen scenarios in the 2020 Oklahoma Testing Ag Performance Solutions (TAPS) sprinkler corn competition. We determined that 63% of the total GHG emission from corn production was associated with in-field activities and that agricultural soil emissions were the overall driving factor. Soil biochemical processes within agricultural soils were expected to contribute an average of 89 ± 18 g CO2-eq kg−1 corn of the total 271 ± 46 g CO2-eq kg−1 corn estimated from these systems. On-site natural gas combustion for agricultural groundwater pumping, pre-field fertilizer production, and pre-field energy production for groundwater pumping were the next most influential parameters on total GHG emissions. Diesel fuel, seed, and herbicide production had insignificant contributions to total GHG emissions from corn production. The model was most sensitive to the modeled GHG emissions from agricultural soil, which had significant uncertainty in the emission factor. Therefore, future efforts should target field measurements to better predict the contribution of direct soil emissions to total GHG emissions, particularly under different managements. In addition, identifying the optimal application rate of irrigation water and fertilizer will help to decrease GHG emissions from groundwater irrigated crops.

Assessment of the sustainability of groundwater utilization and crop production under optimized irrigation strategies in the North China Plain under future climate change

Over-exploitation of groundwater due to intensive irrigation and anticipated climate change pose severe threats to the water and food security worldwide, particularly in the North China Plain (NCP). Limited irrigation has been recognized as an effective way to improve crop water productivity and slow the rapid decline of groundwater levels. Whether optimized limited irrigation strategies could achieve a balance between groundwater pumping and grain production in the NCP under future climate change deserves further study. In this study, an improved Soil and Water Assessment Tool (SWAT) model was used to simulate climate change impacts on shallow groundwater levels and crop production under limited irrigation strategies to suggest optimal irrigation management practices under future climate conditions in the NCP. The simulations of eleven limited irrigation strategies for winter wheat with targeted irrigations at different growth stages and with irrigated or rainfed summer maize were compared with future business-as-usual management. Climate change impacts showed that mean wheat (maize) yield under adequate irrigation was expected to increase by 13.2% (4.9%) during the middle time period (2041–2070) and by 11.2% (4.6%) during the late time period (2071–2100) under three SSPs compared to the historical period (1971–2000). Mean decline rate of shallow groundwater level slowed by approximately 1 m a−1 during the entire future period (2041–2100) under three SSPs with a greater reduction for SSP5–8.5. The average contribution rate of future climate toward the balance of shallow groundwater pumping and replenishment was 62.9%. Based on the simulated crop yields and decline rate of shallow groundwater level under the future climate, the most appropriate limited irrigation was achieved by applying irrigation during the jointing stage of wheat with rainfed maize, which could achieve the groundwater recovery and sustainable food production.

Impacts of Groundwater Management Policies in the Caplina Aquifer, Atacama Desert

Groundwater constitutes one of the main sources used to satisfy the water demands of the different users located in a basin. Current groundwater pumping rates in many cases exceed natural recharge, resulting in the overexploitation of aquifers and the deterioration of water quality. Consequently, many aquifer systems in the world have applied and adapted policies to manage the use of groundwater. In this article, we investigate the impacts of groundwater management policies on the Caplina aquifer located in the Atacama Desert, Peru. To evaluate these impacts, we review policies and regulations implemented during the last 40 years. Likewise, more than 25 scientific investigations that were carried out in this aquifer are reviewed and analyzed to understand its hydrodynamics and hydrochemistry, as well as the impact of climate change, among other aspects. The results, based on scientific evidence, show that the current and future conditions of the groundwater of the Caplina aquifer are not sustainable, and likewise, public policies are not effective for reversing this situation. This leads the aquifer system to a situation in which there is a quality degradation of the water, to a point that may be irreversible.

The development of a hydrogeological conceptual model of groundwater and surface water flows in the Silala River Basin

AbstractFrom 1999 a dispute between Bolivia and Chile concerning the status and use of the Silala River developed. In 2016 it was taken before the International Court of Justice. Over time, a key disagreement between the parties emerged, concerning artificial channels in the headwater wetlands of the Silala River in Bolivia and their impact on the river and groundwater discharge from Bolivia to Chile. To quantify this, a numerical groundwater model was developed by Chile, requiring a hydrogeological conceptual model of the Silala River Basin, reviewed here. This focussed on understanding the groundwater system and its interactions with the Silala River. The data and information used to gain this understanding included geological mapping, drilling, satellite imagery interpretation, geophysical surveys, hydrogeochemical analyses, groundwater level monitoring, surface flow monitoring, and groundwater pumping tests. These were focussed along the course of the river and wetlands. A three‐dimensional geological model of the Silala Basin was based on these investigations. The groundwater model area covers the topographic catchment, plus three adjacent closed (endorheic) topographical catchments to the northeast, which together form the groundwater catchment of the Silala River. The main deep regional aquifer is found in ignimbrite pyroclastic rocks and an interbedded alluvial deposit, but secondary perched aquifers on the flanks of the Silala River ravine contribute to the complexity. Although uncertainty remains, the hydrogeological conceptual model describes the main observed features of the system in a scientifically sound and coherent manner, with appropriate detail to support a credible numerical model.This article is categorized under: Science of Water > Hydrological Processes Engineering Water > Sustainable Engineering of Water

Numerical modeling as a support tool for groundwater permits in the state of Bahia, Brazil

The western region of Bahia State is an important agricultural frontier in Brazil, generating a large increase in requests for groundwater usage in the last decades, mainly through large capacity water wells tapping the Urucuia Aquifer System (UAS). This study aims to develop a groundwater numerical model using the Visual MODFLOW software and the additional packages MODPATH and ZONEBUDGET to evaluate the effects of intensive groundwater pumping in eight possible scenarios of two areas (Central and Eastern) in the Alto Grande - São Desidério rivers sub-basin. Drawdown ranging from 4 to 20 m was observed in the different areas and scenarios. The analysis of the local flow path lines showed that the wells have an area of influence that captures part of the groundwater flow. The water balance indicated that the total volume pumped in the sub-basin did not reach 10% of the recharge in any scenario, considering the entire model domain. The high concentration of irrigation pumping wells in restricted areas resulted in a significant impact on the aquifer, reaching up to 84.6% of the local recharge, a value that is far above what is considered sustainable for the region. Results show that the eastern area is more susceptible to drawdown and changes in flow path lines by pumping. The applied method has proven to be useful to predict the effects of water abstraction on the aquifer before the implementation of projects, improving water resources management. Long-range forecasts and taking into account possible climate changes are also some of the advantages of the method, though it depends on reliable field hydrological and climate data.