Simulation-Optimization for Conjunctive Water Resources Management and Optimal Crop Planning in Kushabhadra-Bhargavi River Delta of Eastern India

Water resources sustainability is a worldwide concern because of climate variability, growing population, and excessive groundwater exploitation in order to meet freshwater demand. Addressing these conflicting challenges sometimes can be aided by using both simulation and mathematical optimization tools. This study combines a groundwater-flow simulation model and two optimization models to develop optimal reconnaissance-level water management strategies. For a given set of hydrologic and management constraints, both of the optimization models are applied to part of the Mahanadi River basin groundwater system, which is an important source of water supply in Odisha State, India. The first optimization model employs a calibrated groundwater simulation model (MODFLOW-2005, the U.S. Geological Survey modular ground-water model) within the Simulation-Optimization MOdeling System (SOMOS) module number 1 (SOMO1) to estimate maximum permissible groundwater extraction, subject to suitable constraints that protect the aquifer from seawater intrusion. The second optimization model uses linear programming optimization to: (a) optimize conjunctive allocation of surface water and groundwater and (b) to determine a cropping pattern that maximizes net annual returns from crop yields, without causing seawater intrusion. Together, the optimization models consider the weather seasons, and the suitability and variability of existing cultivable land, crops, and the hydrogeologic system better than the models that do not employ the distributed maximum groundwater pumping rates that will not induce seawater intrusion. The optimization outcomes suggest that minimizing agricultural rice cultivation (especially during the non-monsoon season) and increasing crop diversification would improve farmers’ livelihoods and aid sustainable use of water resources

Analytical studies of groundwater-head fluctuation in a coastal confined aquifer overlain by a semi-permeable layer with storage

Analytical studies are carried out to investigate groundwater-head changes in a coastal aquifer system in response to tidal fluctuations. The system consists of an unconfined aquifer, a semi-confined aquifer and a semi-permeable confining unit between them. An exact analytical solution is derived to investigate the influences of both leakage and storage of the semi-permeable layer on the tide-induced groundwater-head fluctuation in the semi-confined aquifer. This solution is a generalization of the solution obtained by Jiao and Tang (Water Resource Research 35 (1999) 747-751) which ignored the storage of the semi-confining unit. The analytical solution indicates that both storage and leakage of the semi-permeable layer play an important role in the groundwater-head fluctuation in the confined aquifer. While leakage is generally more important than storage, the impact of storage on groundwater-head fluctuations changes with leakage. With the increase of leakage the fluctuation of groundwater-head in the confined aquifer will be controlled mainly by leakage. The study also demonstrates that the influence of storativity of the semi-permeable layer on groundwater-head fluctuation is negligible only when the storativity of the semi-permeable layer is comparable to or smaller than that of the confined aquifer. However, for aquifer systems with semi-permeable layer composed of thick, soft sedimentary materials, the storativity of the semi-permeable layer is usually much greater than that of the aquifer and its influence should be considered. © 2001 Elsevier Science Ltd. All rights reserved.postprin

Three dimensional simulation of seawater intrusion in a regional coastal aquifer in UAE

Published13th Computer Control for Water Industry Conference, CCWI 2015In this study the vulnerability of the Wadi Ham aquifer, located in the Fujairah Emirate of the UAE, to seawater intrusion (SWI) is assessed using a 3D finite element (FE) model. The numerical model is developed based on available hydrogeological data in real scale. By simulation of the aquifer for the next 10 years and by maintaining the current rates of pumping (in year 2015), the progress of seawater intrusion in year 2025 is followed by further depletion in freshwater storage of the Wadi Ham aquifer. In order to control this problem, the model is subjected to a management strategy involving surface recharge of the aquifer with treated wastewater

A Groundwater Flow Model to Aid in Water Resource Management for the Carraipia Basin in the coastal semi-arid region of La Guajira state (Colombia)

About 160,000 inhabitants live in the 1,600 square kilometers Carraipia River Basin located in northeastern Colombia and northwestern Venezuela. Historically, water has been supplied to the inhabitants in this arid coastal region by shallow dug wells. Water supplied by these wells is frequently of poor quality due to high concentrations of total dissolved solids (TDS). Recently, due to the increasing demand for water, numerous deep wells have been drilled in the region to supply water to rural and urban areas from deep aquifers. Colombian agencies seek more quantitative information on groundwater resources, driven by increasingly severe water shortages over the past decade that have adversely affected the quality of life for the people living in La Guajira state. A groundwater flow computer model has been constructed to provide a tool for assisting with the management of groundwater resources in the Carraipia River Basin. This model is based on geologic maps, hydraulic test wells, geologic field data, and other sparse information to create a highly idealized model of the hydrostratigraphy of this basin. Before creating the three-dimensional groundwater model, stratigraphic columns and cross sections were prepared to guide conceptualization of the idealized groundwater flow model. Available data used to develop the conceptual hydrogeological model includes the following: precipitation data measured in the drainage basin (CORPOGUAJIRA et al., 2006), evapotranspiration data calculated from temperature measurements (CORPOGUAJIRA et al., 2006), hydraulic well tests (Colombian Geological Survey, personal communication), and hydraulic head data measured in shallow wells. The model includes interpreted and conceptualized aquifer parameters, such as hydraulic conductivity (K), and estimated current and future pumping rates. Finally, water table data scattered over the basin area are used to calibrate the model. The regional groundwater system is represented mathematically, using the software ModelMuse and MODFLOW-2005 that discretizes the volume of the basin and the timing of the hydraulic stresses, and balances groundwater flow equations based on input files that define hydraulic stresses. The goal of this project is to use the current stipulated pumping regime in the Carraipia Basin to determine if this groundwater extraction is environmentally sustainable. A secondary goal is to assess how groundwater extraction and other hydraulic stresses impacts the extent of saltwater intrusion. Currently, data are very sparse and topography is poorly constrained. The groundwater model is an idealized representation to establish a starting point for future refinement. In addition, improving the understanding of groundwater flow processes, this model: Can be used to help estimate sustainable yields, Can simulate the impact of different pumping scenarios, Can help identify critical data needed to improve the hydrogeologic characterization of the Carraipia Basin

Hydrogeophysical characterization of coastal aquifers for solution-based modeling, West Coast, South Africa

>Magister Scientiae - MScThe need to improve groundwater security remains critical especially in urban areas where demand for groundwater as an alternative source of water supply increases. Declining trends in availability of surface water because of climate change effects further exacerbates problems of water supply shortage to meet the increasing demand for water, hence the need for groundwater sources. The use of hydrogeophysics data and derivative analysis in understanding aquifer dynamics remains limited and poorly understood therefore, the study argues that when hydrogeophysics data and derivative analysis are not used in aquifer characterization, it results in models that are not solution-based and cannot guide groundwater management. The study was aimed at providing improved understanding on characterization of aquifer dynamics for solution-based modelling while addressing the importance of integrating hydrogeophysics data and derivative analysis in amplifying the heterogeneities that exist in aquifer system

Multi-objective Optimization of Different Management Scenarios to Control Seawater Intrusion in Coastal Aquifers

PublishedThis is the author accepted manuscript. The final version is available from Springer via the DOI in this record.Seawater intrusion (SWI) is a widespread environmental problem, particularly in arid and semi-arid coastal areas. Therefore, appropriate management strategies should be implemented in coastal aquifers to control SWI with acceptable limits of economic and environmental costs. This paper presents the results of an investigation on the efficiencies of different management scenarios for controlling saltwater intrusion using a simulation-optimization approach. A new methodology is proposed to control SWI in coastal aquifers. The proposed method is based on a combination of abstraction of saline water near shoreline, desalination of the abstracted water for domestic consumption and recharge of the aquifer by deep injection of the treated wastewater to ensure the sustainability of the aquifer. The efficiency of the proposed method is investigated in terms of water quality and capital and maintenance costs in comparison with other scenarios of groundwater management. A multi-objective genetic algorithm based evolutionary optimization model is integrated with the numerical simulation model to search for optimal solution of each scenario of SWI control. The main objective is to minimize both the total cost of management process and the total salinity in aquifer. The results indicate that the proposed method is efficient in controlling SWI as it offers the least cost and least salinity in the aquifer

Modeling the Mitigation of Seawater Intrusion By Pumping Brackish Water from the Coastal Aquifer Of Wadi Ham, UAE

The control and management of seawater intrusion in coastal aquifers is a major challenge in the field of water resources management. Seawater intrusion is a major problem in the coastal aquifer of Wadi Ham, United Arab Emirates caused by intensive groundwater abstraction from increased agricultural activities. This has caused the abonnement of salinized wells and ultimately affected farming activities and domestic water supply in the area. In this study, the 3D finite element groundwater flow and solute transport model, FEFLOW was used to simulate pumping of brackish water from the intrusion zone to control seawater intrusion in the aquifer. The model was calibrated and validated with available records of groundwater levels and salinity distribution. Different simulation scenarios were conducted to obtain optimum pumping locations, rates as well as number of wells. It was found that pumping at a distance of 1500 m from the shoreline at 500m3/day using 16 installed wells is the optimum simulation. A comparison between scenarios of non-pumping and pumping was conducted. Results showed an increased in salt concentration in groundwater under the non-pumping scenario while it decreased under the pumping scenario. Under non-pumping scenario isoline 35,000 mg/l was observed to have intruded into the eastern southern part of the aquifer while maximum isoline observed for the same area under pumping scenario was 20,000 mg/l. This result showed an overall improvement in salt concentration in groundwater distribution and ultimately halted seawater intrusion in the aquifer

Numerical error in groundwater flow and solute transport simulation

Models of groundwater flow and solute transport may be affected by numerical error, leading to quantitative and qualitative changes in behavior. In this paper we compare and combine three methods of assessing the extent of numerical error: grid refinement, mathematical analysis, and benchmark test problems. In particular, we assess the popular solute transport code SUTRA [ Voss, 1984 ] as being a typical finite element code. Our numerical analysis suggests that SUTRA incorporates a numerical dispersion error and that its mass-lumped numerical scheme increases the numerical error. This is confirmed using a Gaussian test problem. A modified SUTRA code, in which the numerical dispersion is calculated and subtracted, produces better results. The much more challenging Elder problem [ Elder, 1967 ; Voss and Souza, 1987 ] is then considered. Calculation of its numerical dispersion coefficients and numerical stability show that the Elder problem is prone to error. We confirm that Elder problem results are extremely sensitive to the simulation method used.Juliette A. Woods, Michael D. Teubner, Craig T. Simmons and Kumar A. Naraya

Optimizing operation and design of aquifer storage and recovery (ASR) wellfields

2019 Fall.Includes bibliographical references.Sustained production of groundwater from wells in wellfields can lead to declining water levels at production wells and concerns regarding the sustainability of groundwater resources. Furthermore, minimizing energy consumption associated with pumping groundwater is a growing concern. Aquifer Storage and Recovery (ASR) is a promising approach for maintaining water levels in wells, increasing the sustainability of groundwater resources, and minimize energy consumption during groundwater pumping. Therefore, studying the importance of ASR in sustaining water levels and minimizing energy consumption is critical. In the first part of this dissertation, an analytical model relying on superposition of the Theis equation is used to resolve water levels in 40 wells in three vertically stacked ASR wellfields. Fifteen years of dynamic recovery/recharge data are used to obtain aquifer and well properties. Estimated aquifer and well properties are used to predict water levels at production well. Close agreement between modeled and observed water levels support the validity of the analytical model for estimating water levels at ASR wells. During the study period, 45 million m³ of groundwater is produced and 11 million m3 is recharged leading to a net withdrawal of 34 million m³ of groundwater. Rates of changes in recoverable water levels in wells in the Denver, Arapahoe and Laramie-Fox Hill Aquifers are 0.20, -0.91, and -3.48 m per year, respectively. To quantify the benefits of recharge, the analytical model is applied to predicting water levels at wells absent the historical recharge. Results indicate that during recovery and no-flow periods, recharge has increased water levels at wells up to 60 m compared to the no-recharge scenario. On average, the recharge increased water levels at wells during the study period by 3, 4, and 11 m in the Denver, Arapahoe, and Laramie Fox-Hills Aquifers, respectively. Overall, the analytical model is a promising tool for advancing ASR wellfields and ASR can be a viable approach to sustaining water levels in wells in wellfields. In the second part of this dissertation, a simulation-optimization model (ASRSOM) is developed to optimize ASR wellfield operations. ASRSOM combines an analytical hydraulic model and a numerical optimization model to optimize wellfield operations. The objective function used to minimize energy consumption φ (L⁴) is the temporal integral of the products of temporally varying total dynamic head values and pumping rates. Comparison of ASRSOM results to work by others for idealized aquifer operations supports the validity of ASRSOM. Four scenarios were simulated to evaluate the role that optimization of operations and aquifer recharge play in reducing the energy required to lift groundwater out of aquifer. A 10-year study period is considered using data from a municipal ASR wellfield. Optimization decreased φ by 19.6%, which yields an estimated reduction of 2,179 MW hours of power and 1,541 metric tons of atmospheric carbon. For the condition considered, recharge reduced power by 1%. The limited benefit of recharge is attributed to the small recharge volume in the case study and the short duration of the analysis. Additional opportunities to address economic and environmental impacts associated with lifting groundwater out aquifer include optimizing the position of wells and factors controlling total pumping head. In the third part of this dissertation, the sensitivity of well-spacing in ASR wellfields to critical parameters is studied. The parameters studied are aquifer transmissivity and storativity, wells flowrate and the frequency of recharge and recovery. It has been found that larger well-spacing are appropriate for lower transmissivity and storativity, and larger wells flowrate and frequency. More work is needed to fully understand the optimal well-spacing of wells in ASR wellfields associated with more realistic storage and recovery schedules, and more complex wellfields. Overall, work supported the possibility that wells in ASR wellfields can be spread more closely than wells in conventional production wellfields

NCMA GROUNDWATER MODEL USING USGS MODFLOW-2005/PEST

A numerical model for the NCMA aquifer complex is presented. The objective of the study is to develop a numerical groundwater model for the NCMA aquifer system to enhance the understanding of subsurface groundwater flow. Infiltration, streamflow, pumping, and return flows are implemented to characterize the aquifer complex over time. The numerical model is calibrated to municipal and monitoring well data, average monthly water balances, and hydraulic contours. Transient aquifer inflows and outflows are assessed in the results of the study and are compared to balance terms from previous studies. The 2007 Todd Engineers Study subsurface inflows and outflows generate well hydrographs that have greater heads than observed data. Calibration to well hydrographs generated increased subsurface outflow values and decreased subsurface inflow values. It is possible that approximately 250 AFY is leaving aquifer storage