Irrigation Wells Research Articles

Arsenic contamination of irrigation wells and associated human health hazards in the Punjab plains of Pakistan

In the present study, the tubewell water quality, emphasizing on As contamination, were investigated in the Punjab plains of Pakistan. The Na-Cl water type is dominated in Doabs (Rechna and Chaj) whereas Ca-HCO3 water type is dominated in Ravi flood plain. Concentrations of As in well water (65 ± 32 μg/L) are higher in the floodplains of the Ravi River compared to the Chenab (13 ± 9 μg/L) and Jhelum (4 ± 5 μg/L) rivers, as well as in the intervening Rechna (6 ± 6 μg/L) and Chaj doabs (0.8 ± 0.2 μg/L). The average Hazard quotients (HQ) is 9.09E+00 and Potential Cancer Risk (CR) is 4.09E−03 in Ravi flood plain which indicates the potential health risk to the consumers of well water for drinking purposes and also long term irrigation with this water will result As accumulation in paddy soil. Based on average values, the Sodium Adsorption Ratio (SAR), Magnesium Hazard (MH), %Sodium (%Na) and Kelly Ratio (KR) follows the sequence Rechna Doab>Chaj Doab>Chenab floodplain>Jhelum floodplain>Ravi floodplain in 5 geographic units, suggesting low salinity water in floodplains and saline water in Doabs.

A Surrogate Water Quality Index to assess groundwater using a unified DEA-OWA framework.

In this paper, we introduce a new approach, based on a unified framework incorporating Data Envelopment Analysis (DEA) and Ordered Weighted Averaging (OWA), for assessing water quality in contextual settings that involve a large number of hydrochemical parameters. In order to enhance discrimination among water sources, the DEA model is adopted with data-driven input variables, called "surrogate optimistic closeness values," computed through an aggregation procedure that includes the observed values of the hydrochemical parameters with OWA weights. The proposed DEA-OWA methodology has been employed to assess the quality of 51 water samples, collected from irrigation wells in Sereflikochisar Basin, Turkey, by means of 19 hydrochemical parameters. Using different subjectivity levels, the Surrogate Water Quality Indices (SWQIs) that are produced are proven effective in enhancing discrimination among the water sources while enabling a more robust water quality-based ranking. The k-means analysis has been used for clustering the water quality of the wells into Excellent, Good, Permissible, and Unsuitable rather than using pre-set boundaries. Only one water source has been identified as Excellent, whereas 17.65%, 45.10%, and 35.29% of the sampled wells, respectively, are categorized with Good, Permissible, and Unsuitable water quality. Inferred from wells' location, the results suggest that the groundwater might be drastically affected by saline water intrusion from Lake Tuz. The latter conclusion has been corroborated through a Tobit regression analysis.

Improving Energy Efficiency of Irrigation Wells by Using an IoT-Based Platform

The irrigation sector has undergone a remarkable transformation in recent decades due to the application of pressurized water distribution technologies, improving the management of limited water resources. As a result of this transformation, irrigation has become, together with agricultural machinery, the primary consumer of energy within the agri-food sector. Furthermore, the energy cost of operating pumping equipment during a farming season represents 30–40% of the crop’s total cost. For this reason, one of the most interesting challenges in this scope is that of improving energy efficiency and reducing economic costs so that productive work become more and more competitive. Energy audit makes possible to determine the efficiency of installations, and enables to determine energy saving protocols (requirements), for this reason the aim of this article is to carry out these by using IoT-based systems. The proposed system improves decision-making on agricultural pumping management by classifying wells’ efficiency and integrating the data sets that determine their efficiency into a single information model. The system monitors energy efficiency according to different parameters such as: infrastructure, energy consumption, electric rates, manometric height or type of installation, making it possible to enhance each pumping operation’s decisions. This solution has been deployed in an irrigation community in southeast Spain whose results have warned about the lack of efficiency in two of its wells: in one of them it is proposed that they be replaced, due to the high cost of pumping water, and in the other, hydraulic mechanisms are implemented to improve the water-energy binomial.

Irrigation well water: Essential nutrient contents and other properties

AbstractWater nutrient concentrations and other properties were surveyed by sampling water from 642 irrigation wells in Nebraska. The amount of Ca, Mg, S, and Cl applied in irrigation exceeds removal in 15 Mg ha−1 of corn (Zea mays L.) grain harvest for most wells. Irrigation supply exceeded corn grain harvest removal of K, B, Mn, and Mo for >20% of the wells. The supply of P, Zn, Cu, Fe, and Mo was generally very low but sufficient with some wells to be considered in nutrient management plans. The median level of nitrate N was 4.4 mg kg–1 with 25% of the wells having >10 mg kg–1 NO3–N, which is above the suitability limit for human consumption. The agricultural lime equivalent applied with 1 or 2 Ml of irrigation was enough to neutralize the acidifying effect of 200 kg ha−1 of fertilizer N for 70 or 89% of the wells. Nutrient and lime supply was relatively low for Sandhills wells and relatively high for wells in river valleys of <30.5 m (100 ft) depth. No wells had excessive Na levels but 0.3% of the wells had high salinity levels. A grouping of wells into 11 aquifer–geology–depth categories accounted for >20% of the variation for most water properties but much variation occurred within categories. Sampling of the well water is needed for optimized nutrient and soil management. Information on nutrients supplied through irrigation should be complemented by regular soil testing and the use of recommended nutrient management guidelines.

Моделирование процессов фильтрации технологических растворов при блочном подземном выщелачивании

PAO “Priargunsky Production Mining and Chemical Association” has been working on reserves of uranium deposits of the Streltsovsky ore field for more than 50 years. During this period, most of the rich ores have been worked out by traditional mining and physical technology. The share of poor and ordinary ores remains significant, but traditional technology does not provide the necessary level of profitability. Therefore, the widespread introduction of physicochemical technology: underground block (BPV) and heap leaching (KV) can be a decisive moment in the continuation of the operation of these deposits. The applied technology of underground block leaching has one significant drawback – a low rate of uranium recovery into a productive solution, which significantly reduces the effectiveness of this technology in the development of poor uranium deposits. To increase the yield of uranium into the productive solution, it is necessary to analyze the entire preparation and leaching process and establish the main reasons for the low rates of transition of uranium to a mobile state. For this purpose, it is proposed to simulate the underground leaching process by building visual models of halos spreading of solutions along shrinked ore mining mass accumulated in an underground chamber. During the simulation, it was found that the distribution of the size classes of the broken ore pieces in the chamber can be predicted at the stage of drilling and blasting operations, and when determining the line of least resistance W and the distance between the ends of the wells, take into account the diameter of the controlled crushing zone R_p. At the same time, 3 zones of granulometric compositions are formed: a re-grinding zone, an optimum zone and a non-carbarite exit zone. The flow of solutions through these zones will differ the more significantly, the higher the height of the chamber. In a zone with larger crushing, an almost steep distribution of the solution spreading front is expected. Accordingly, the smaller the fraction, the lower the front to the horizontal is. The following functions are offered to simulate filtering processes: – it is possible to control the flow of working solutions to the fan of irrigation wells in order to achieve optimal leaching parameters, i.e. to quickly control the process; – knowledge of the law of distribution of irrigation flares makes it possible to select the optimal grid of location of single sprinklers

Construction of vertical drainage wells using corrosion resistant materials

Vertical drainage wells in terms of construction technology and design do not differ from wells for irrigation. They are not deeper in-depth than irrigation wells and are generally 40-70 m. The main task of vertical drainage wells is land reclamation. They, depending on natural and economic conditions, serve on 5-120 hectares of area. In many areas, vertical drainage wells serve a dual purpose; land reclamation and irrigation of agricultural crops. Water intake wells, including vertical drainage wells, are characterized by a decrease in their flow rates during operation. To ensure the stable operation of the irrigation and drainage system, where water intake wells are operated, repair and restoration work is carried out on them, aimed at increasing flow rates. For the construction of vertical drainage wells in the Sirdarya river basin, steel pipes and filters are mainly used, which corrode in an aggressive environment. In the water intake zone of the well and the metal corrosion process, the colmatation process also occurs. All of them are the main reasons for the decline in well production rates. The carried out repair and restoration measures are aimed at destroying the structure of corrosion and clogging products. In practice, mechanical, physical, biological, and chemical methods are used to clean the filters of water intake wells. They all have their own technology and equipment. However, all these works do not exclude the repeatability of the process. Repetitive workover will come to ineffective, the stage of good concertation is approaching. It is known that polymeric materials do not corrode. They work steadily in aggressive environments. To prevent the corrosion process, polymeric-seam pipes were used as a filter frame and a casing for the construction of vertical drainage wells. Two pilot wells were built on the territory of the Chiyili district of the Kyzylorda region of the Republic of Kazakhstan. The wells were drilled with a rotary drilling unit with backwash. Pure water (irrigation) was used as drilling fluid. To form a gravel pack in the annular zone of the casing, gravel-sand material from the Jailma quarry was used. The material was brought by rail and road transport. Pipe sections were prepared on the surface of 10 meters. Steel rings were put on the pipe from both ends of each section; their connection in the barrel was made by electric welding. The results showed that in the initial period of operation, a decline process was observed. In further exploitation, the well flow rate stabilized. As a result of construction using pipes and filters made of polymer material, the effect was achieved in terms of water volume more than 3 times and in terms of service life 4.2 times compared to a metal filter well.

Optimizing Groundwater Aquifers Potential in The Development of Irrigation Wells for Agriculture Using Geo-Electrical Method

The identification of shallow groundwater aquifers is demanded to sustain the balance of utilization in agriculture and anticipate frictions that can occur due to the overlapping usage of groundwater resources. This study is aimed to identify the potential of groundwater resources based on the thickness and depth of the groundwater aquifer. Geoelectric resistivity methods have done with vertical electrical sounding (VES) and horizontal profiling techniques (2D mapping). The VES data acquisition was carried out with a Schlumberger array while 2D mapping by alpha Wenner array. Inversion results of vertical electrical sounding (VES) show that groundwater resistivity values in sedimentary rocks ranged from 1 to 100 ?m and in igneous rocks between 0.5 - 150 ?m. The results of 2D Resistivity Mapping also show that shallow aquifer depth ranged from 1 to 5 m with a thickness ranged from 15 m to more than 70 m. Meanwhile, bedrock depth ranged from 20 to 150 m with a pattern deeper to the west. Furthermore, the potential of groundwater aquifers in the development of irrigation wells for agriculture should be carried out in the western part of the study area.
 
 Keywords: Groundwater, Shallow Aquifer, Rock Resistivity, Irrigation Well, Geo-Electrical Sounding.

Status of the Use of Groundwater during the Dry Season at 5 and 7 Blocks of the Irrigated Rice Plain of Bama, Burkina Faso

Water insufficiency in the irrigation canals during the dry season in the rice-growing plain of Bama means that barely 20% of the plots is cultivated with rice during this period, causing losses of over 1,500,000. US $ per year. So, groundwater is used as an alternative by some producers without control. This study aims to assess the current use of groundwater for off-season production in blocks 5 and 7 of the Bama plain. The diagnosis was made during the 2019 dry season by means of focus group, then an individual survey in order to inventory the sinks and speculations produced. Then, around twenty large-diameter rice irrigation wells were followed to determine the volumes of water supplied. The results showed that, the small wells are mainly intended for manual irrigation of market gardening during the cold dry season and large-diameter wells for pumping rice cultivation in the hot dry season. Finally, over-irrigation of more than 2.5% of rice needs was observed.

Google Earth Imageries for Validating Groundwater Recharge Zone in Basaltic region

Abstract A majority of the existing groundwater potential studies in the literature lack adequate validation. In developing countries, it is attributed to many reasons including- poor/limited data on water yield, sparse spatial and temporal data on wells, lack of data protocol/sharing, a weak ground water governance structure such as disparate agencies, lack of registration/georeferencing of irrigation wells. A rapid, simple and replicable approach is proposed to overcome these difficulties using Google Earth imageries for visual interpretation, interwined with cadastral data and telecommunication for a representative block located in basaltic region of Maharashtra, India. Each of 1684 irrigation well in the study area was enumerated, its irrigation area estimated and verified through available records, field visits, telecommunication with well owners and georeferenced to link with land parcel identification number and build well information system. Functional and defunct wells were distinguished using deacadel timeline data. Nine major biophysical and environmental factors namely geomorphology, soil, land use land cover, slope, lineament density, drainage density, topographical wetness index, curvature and aspect were analyzed to asses the groundwater recharge potential (GWP). The GWP zones were verified using the georeferenced enumeration data on wells, their density and area irrigated per unit well. The number of wells, functional well density followed an order high < moderate < moderate to poor < poor to nil, i.e. highest density (0.034/ha) in high potential zone and lowest density (0/ha) in poor to nil potential zone. Number of defunct wells also exhibited linear correspondence with least share (51%) in ‘high’ potential zone and higher share (76%) in ‘moderate to poor’ potential zone. It is concluded that Google Earth imageries provide direct and conclusive well enumeration, its irrigated area and therby accurate means of evaluating GWP zonation. It has immense potential for use in many countries where historical data are inadequate to assist groundwater management/governance.

How to Meter Agricultural Pumping at Numerous Small-Scale Wells?—An Indirect Monitoring Method Using Electric Energy as Proxy

The large number of users and the small scale of wells greatly complicate monitoring of groundwater abstraction in areas of intensive pumping by numerous smallholders such as in the North China Plain. This paper presents a study in a typical county in the North China Plain. It discusses the application and challenges of an indirect, energy-based approach to groundwater abstraction monitoring. Intensive field experiments at individual wells were carried out to provide a basis for the conversion from electric energy consumption to groundwater abstraction and to explore the feasibility of direct and indirect abstraction monitoring methods in the study area. The results show that the main challenge of electricity-to-water conversion lies in the large spread of conversion factors between wells. The conversion error at an individual well is found to be less than 20%. The same accuracy is achieved on spatially aggregated levels by testing only a small number of wells. Trade-offs can be made to obtain groundwater abstraction estimates at the required accuracy and with reasonable efforts regarding data collection. The analysis shows that energy-based groundwater abstraction monitoring outperforms direct water metering with respect to cost and robustness. It provides satisfactory data accuracy and equitability in regions where irrigation wells are powered by electricity.

A Bayesian framework to unravel food, groundwater, and climate linkages: A case study from Louisiana.

Advancing our understanding of the connections among groundwater, food, and climate is critical to meet global food demands while optimizing water resources usage. However, our understanding of the linkages among groundwater, food, and climate is still limited. Here, we offer a Bayesian framework to simulate crop yield at a regional scale and quantify its relationships and associated uncertainty with climate, groundwater, agricultural, and energy-related variables. We implemented the framework in the rice-producing regions of Louisiana from 1960-2015. To build a parsimonious model, we used a probability-based variable selection approach to detect the key drivers of rice yield. Rice yield increased, groundwater declined, and area planted declined or did not change over 56yrs. The number of irrigation wells, groundwater level, air temperature, and area planted were found to be the key drivers of rice yield. The regression coefficients showed that rice yield was positively related to groundwater level, and negatively related to area planted and the number of irrigation wells. The limited influence of N fertilizer was noted on rice yield for the period when fertilizer data were available. The inverse relationship between rice yield and area planted pointed to the adaption of efficient crop management practices that maintained or increased yield, despite the decline in area planted. The farmers' ability to install irrigation wells during droughts sustained the yields over long-term but not short-term. This decline in rice yield in response to drought over the short-term might explain the negative relation between yield and irrigation wells. Overall, this work highlighted the uncertainty in relationships between rice yield and key drivers and quantified the intimate connection between food and groundwater. This work may have implications for managing two highly competing commodities (i.e., groundwater and food) in agricultural regions.

Adoption of Water-Conserving Irrigation Practices among Row-Crop Growers in Mississippi, USA

This article identifies irrigated row-crop farmer factors associated with the adoption of water-conserving practices. The analysis is performed on data from a survey of irrigators in Mississippi. Regression results show that the amount of irrigated area, years of education, perception of a groundwater problem, and participation in conservation programs are positively associated with practice adoption; while number of years farming, growing rice, and pumping cost are negatively associated with adoption. However, not all factors are statistically significant for all practices. Survey results indicate that only a third of growers are aware of groundwater problems at the farm or state level; and this lack of awareness is related to whether farmers noticed a change in the depth to water distance in their irrigation wells. This evidence is consistent with a report to Congress from the Government Accountability Office (GAO) that recommends policies promoting the use of: (1) more efficient irrigation technology and practices and (2) precision agriculture technologies, such as soil moisture sensors and irrigation automation.

Groundwater Flow-Modeling and Sensitivity Analysis in a Hyper Arid Region

Groundwater modelling is particularly challenging in arid regions where limited water recharge is available. A fault zone will add a significant challenge to the modelling process. The Western Desert in Iraq has been chosen to implement the modelling concept and calculate the model sensitivity to the changes in aquifer hydraulic properties and calibration by researching 102 observations and irrigation wells. MODFLOW-NWT, which is a Newtonian formulation for MODFLOW-2005 approaches, have been used in this study. Further, the simulation run has been implemented using the Upstream-Weighting package (UPW) to treat the dry cells. The results show sensitivity to the change of the Kx value for the major groundwater discharge flow. Only about 7% of the models from the region can be irrigated utilizing greenhouses supported by external recharge.

IRRIGATION SYSTEM IN DHARWAD DISTRICT: A GEOGRAPHICAL ANALYSIS

Irrigation in India has been practiced from ancient times and irrigation tanks and wells are a familiar feature of the India landscape to supplement and conserve the rainfall. Artificial lakes and canals that dot the country in the hundred are centuries old and some of them has served for more than thousand years. Storages and their water courses are common in south, central and eastern India. Hindu monarchs and the Mughal emperors later on, the Britishers undertook a large number of irrigation works. Water is needed in almost every sphere of human activity. Irrigation through major and medium canal systems was a key component of green revolution that transformed India and made the spectre of famines in India history. Irrigated agriculture is thus responsible for the rapid improvement in the agriculture productivity in the 1960’s, 70s, and 80’s. There is a marked difference in the levels of contribution from agriculture in the rain-fed and the irrigated areas. In general irrigation is seen to be affecting poverty by increasing returns to the physical, human and social capital; integrating the poor with factor, product and information markets and improving the overall national growth rates. Among taluks, the area of corps, production and productivity of crops are higher in Dharwad and Navalgund taluks owing to more area under irrigation. Even horticulture crops are also more in these two taluks as compared to other taluks as a consequence of more area under irrigation. The available utilizable water resource of the District, viz: Dharwad, Hubli, Kalghatgi, Kundagol, Navalgund; is considered insufficient to meet all the future needs. Under such a situation, in order to face the challenge of water deficit, apart from accelerating pace of development of available utilizable water resources, all out efforts, on the part of people from every walk of life, would need to be made to conserve every drop of water and improve efficiency in all areas of water use. Keywords: Irrigation; Sources of Irrigation; Yielding; Cropping; Agriculture Economy

Interactions of Dimethylarsinic Acid, Total Arsenic and Zinc Affecting Rice Crop Management and Human Health in Cambodia

Background.In parts of Cambodia and in many other parts of the world, irrigation of rice with groundwater results in arsenic (As) accumulation in soil and rice, leading to health concerns associated with rice consumption. At times, some As is present as relatively nontoxic, non-regulated, dimethylarsinic acid (DMA). Low levels of zinc (Zn) have been found in rice from Bangladesh, Cambodia, and China where As levels in rice are high. Furthermore, there have been claims that Zn deficiency is responsible for stunting the growth of children in Cambodia and elsewhere, however in rural Asia, rice is the major source of Zn. Current data are inadequate for both Zn and DMA in Cambodian rice.Objectives.The present study aimed to provide a preliminary evaluation of the relationship between the content of Zn and DMA in rice grain in Preak Russey, an area with elevated levels of As in groundwater and to improve the management of Zn deficiency in rice.Methods.Rice agriculture was evaluated along the Mekong River in Cambodia. Analyses for metals, total As, and As species in rice and water were conducted by inductively coupled plasma mass spectrometry. Analysis of total Zn and As in soils and total Zn in rice were analyzed using X-ray fluorescence (XRF) spectrometry.Results.Rice in Preak Russey had Zn concentrations less than a third the level recommended by the United Nations World Food Programme. There was a significant (p < 0.05) negative correlation between the Zn content of rice and DMA in rice with the lowest Zn and highest DMA levels occurring near irrigation wells, the source of As.Conclusions.The highest levels of DMA in rice were associated with Zn deficiency in rice.Competing Interests.The authors declare no competing financial interests

Geochemical Assessment of Potential Sources for Nitrate in the Wasia Aquifer, Al Kharj Area, Central Saudi Arabia

Nitrate (NO3−) represents one of the major groundwater constituents with increasing distribution and concentration in the Kingdom of Saudi Arabia. This study aimed to determine potential sources of nitrate in the Early to Late Cretaceous Wasia aquifer system at the Al Kharj area (Central Saudi Arabia) by an integrative approach using groundwater geochemistry, nitrate isotopes (15N–NO3 and 18O–NO3), and tritium (3H) measurements. The lowest saline groundwater samples (TDS = 1400–2000 mg/L) from the peripheral zone were representative for pristine groundwater from the Wasia aquifer with nitrate concentrations below 20 mg/L and low 18O–NO3 ratios (8.7–20.6‰) but enriched 15N–NO3 values (up to 10.8‰). In contrast, 11 out of 34 analyzed water samples from irrigation wells and cattle watering wells exceeded the World Health Organization (WHO) drinking water guideline value for nitrate of 50 mg/L with maximum concentrations of up to 395 mg/L. Nitrate fertilizers and atmospheric deposition are the main sources of nitrate in groundwater in the eastern and northern sections of the study area. The combination of elevated salinities (4940–7330 mg/L), NO3 (111–395 mg/L), boron (516–1430 μg/L), and enriched 18O–NO3 (21.7–25.8‰) ratios with depleted 15N–NO3 (5.7–7.6‰) confirm the local influx of evaporated irrigation water with remnants of dissolved fertilizer into the Wasia groundwater system. There was no evidence for the influx of animal or human wastes from adjacent dairy, poultry, and housing infrastructures. Tritium concentrations below the detection limit of 0.8 TU for most borehole samples implied the absence of recent natural recharge. The estimated annual average N influx of 3.34 to 6.67 kg/ha to the Wasia aquifer requires a combination of atmospheric deposition and anthropogenic sources (mainly nitrate fertilizers) to increase the nitrogen content of the Wasia aquifer.

A Study on the Cause of Layered Seawater Intrusion in the Daqing River Estuary of Liaodong Bay, China

Groundwater over-pumping in estuary cities leads to a series of groundwater environmental problems that seriously restricts economic development. On the basis of field investigation and long-term monitoring data analysis, a three-dimensional numerical model was built in the estuary of the Daqing River in Liaodong Bay, China. The Quaternary overburden can be generalized into five layers according to particle composition and parameters in the vertical direction. There are many scattered irrigation wells pumping in the second layer, and three water source areas mainly pumping groundwater in the fourth layer. Long-term over-pumping in multi-layered aquifers causes onshore layered seawater intrusion. The laws of layered intrusion under the layered pumping were calculated and analyzed with SEAWAT-2000, and the sensitivity was analyzed with the Sobol method. Results showed that the intrusion area had an obvious layered law. Layered pumping directly affected the layered intrusion area, as different permeability, tide and barrage further affected it. The prediction study showed that the cone of depression recovered after the pumping-limit of water source areas, and the intrusion area started to retreat in the fourth layer. At that time, the pumping quantity of irrigation wells became the main reason for the increase of the intrusion area. If the water source areas are used to bear part of the irrigation demand, so as to reduce the pressure of pumping in the second layer, the overall intrusion area can be reduced by about 0.23 km2 under the same pumping quantity.

Real Investment on Ground Water in Cauvery Basin Areas of Karnataka- An Economic Analysis

In this study, irrigation wells located under canal command (GWCI) (Gadabanaalli), the irrigation wells located under tank command (GWTI) (Echanur), receiving the Hemavathy river water, with a water spread of 363 acres and another village Kibbanahalli where groundwater wells are located independently (called groundwater under sole irrigation GWSI), which depend only on rainfall source have been considered. Only farmers possessing irrigation wells in each of the three scenarios were chosen. A random sample of 35 farmers was drawn from each of the three scenarios, thus, totaling 105 for the purpose of this study. It was observed that the real investment was falling over the years with a range of Rs. 3137 to Rs. 6255 even though the nominal investment ranged between Rs. 19100 and Rs. 66600 for farmers in GWTI. Real investment on irrigation wells shows a declining trend in all the three situations. Thus, the real cost of groundwater is falling over time not exhibiting ricardian scarcity. In GCTI farmers, the real investment for working well was falling over the years with a range of Rs. 1815 to Rs. 6225 even though the nominal investment ranged between Rs. 20600 and Rs. 73987, the mean real investment per well was Rs. 5103, and the mean nominal investment per well was Rs. 40352. Considering the nominal cost of extraction of groundwater, it was clear that there was an increasing trend due to inflation and associated factors. However, the real cost of extraction was found to be consistent over the years.

Mechanisms of groundwater arsenic variations induced by extraction in the western Hetao Basin, Inner Mongolia, China

High arsenic (As) groundwater has posed a serious threat to human health. Due to the complex spatial-temporal distributions of dissolved As, the influence of groundwater extraction on As enrichment has attracted great attention. To ascertain spatial-temporal variations in dissolved As and driving mechanisms impacted by extraction, we monitored groundwater levels and chemicals in different aquifers in the western Hetao basin, China. Results revealed that groundwater levels decreased during irrigation season in both shallow (<40 m below land surface (bls)) and deep (>42 m bls) aquifers, and the decreases in deep aquifer were more evident. During irrigation, the estimated proportion of recharge from shallow groundwater to affected deep groundwater (around 45 m bls) increased from 21% to 53% in the distal of the alluvial fan and sharply from 53% to 86% in the flat plain. In the distal of the alluvial fan, the vertical recharge of shallow groundwater with low As concentrations (<10 μg/L) directly decreased dissolved As concentrations in deep groundwater, and the introduced oxygen-containing groundwater promoted As fixation. In the flat plain, As concentrations of affected deep groundwater increased by around 80% during irrigation, which may result from the direct introduction of dissolved As, labile organic matter and high Na/Ca0.5 molar ratio from shallow groundwater. The latter two promoted As release by enhanced dissimilatory reduction of Fe oxyhydroxides and As desorption, respectively. The two-year monitoring data of conservative tracers and dissolved As concentrations in irrigation wells also validated the hypothesis. This study highlights the different variation patterns of deep groundwater As concentration impacted by extraction in different hydrogeological units, and provides an insight into mechanisms of As variations impacted by anthropogenic activity.

Aquifer storage and recovery, and managed aquifer recharge of reclaimed water for management of coastal aquifers

The hydrological and economic feasibility of aquifer storage and recovery (ASR) of excess desali-nated water and managed aquifer recharge (MAR) using tertiary treated wastewater (TTWW) to manage stressed coastal aquifers in Oman has been studied numerically using the code, MODFLOW 2005 and the different transport packages MT3DMS, and MODPATH. The current ASR study aims to assess the feasibility of saving and recovering water for the purpose of supply to the city of MUSCAT during high demand periods by banking excess-desalted water during winter and recover it during the rest of the year. The second objective of the study is to explore the feasibility of MAR using TTWW to mitigate salinity in two costal aquifers in North of Oman exploited for different purposes: domestic water supply (Al-Khod aquifer), and for irrigation purposes (Jamma aquifer). ASR in the Al-Khod Aquifer was explored using Simulation Optimization multi-objective modeling using evolutionary algorithm NSGA-II (namely, the Non-dominated Sorting Genetic Algorithm-II), to generate the set of Pareto optimal solutions according to recharging scenarios. The results show that the potential net benefit of storage and recovery might reach as high as 17.80 million/year. The maximum profitable volume that can be recharged into the aquifer, given the limited number of wells and their locations, is estimated at 8.4 Mm3/year, which is lower than the current excess estimated of 10 Mm3/year. For MAR using TTWW, different managerial scenarios were simulated and analysis of the results reveals that the Jamma aquifer will further deteriorate in the next 20 years if it remains poorly managed. The groundwater level will decline further to exceed 3 m on average, and the iso-concentric salinity line of 1,500 mg/L will advance 2.7 km inland that will severely affect farming activities in the area. However, MAR using TTWW when integrated with the management of groundwater abstraction (e.g., smart water meter, higher irrigation efficiency to reduce the abstraction rate) becomes hydrologically feasible to augment the aquifer storage and controlling seawater intrusion, and hence sustains farming activities. The economic analyses of such situation recommend: (1) injecting TTWW in the vicinity of irrigation wells; (2) investing in smart water meters and online control of pumping from the wells to reduce the abstraction rate by 25; and (3) a combination of both are feasible scenarios with positive net present values. Recharge in upstream areas is found not economically feasible because of high investment cost of the installation of pipes to transport the TTWW over a distance of 12.5 km. Because the financial resources for investments are limited, scenario (2) shows a Net Benefit Investment Ratio of 4.41 (i.e., investment of a 1 yields 4.41). Although option (3) shows the lowest Net Benefit Investment, it is very attractive from a social perspective because it entails an integrated demand and supply management of groundwater. Farmers are requested to reduce pumping, and the gov-ernment will invest in injecting TTWW to improve groundwater quality in the vicinity of irrigation wells and to form a hydrological barrier to control seawater intrusion in the long run. The primary objective of MAR for the Al-Khod aquifer is to increase the urban water supply and to sustain the aquifer service with the lowest possible damages from seawater intrusion. A number of managerial scenarios were simulated and progressively developed to reduce seawater intrusion and outflow of the groundwater to the sea. An economic analysis was conducted to characterize the trade-off between the benefits of MAR and seawater inflow to the aquifer under increased abstraction for domestic supply. The results show that the abstracted volume for domestic supply can be doubled under MAR practices if irrigation wells are properly managed and public wells are better located. Even though injection of TTWW is more expensive (due to the injection cost), will result in higher benefits. The results indicate that managing the aquifer would produce a net benefit ranging from 8.22 million to 15.21 million compared with 1.57 million with the current practice. MAR using TTWW is feasible to develop water resources in arid regions, and the best scenario depends on the decision maker’s preference when weighing the benefits of MAR and the level of damage to the aquifer. MAR, as a smart water governance technology, mitigates stresses on aquifer systems in arid zones, maximizes the benefit of using groundwater for both agricultural and domestic purposes while minimizing the adverse socio-hydrological and agricultural consequences of mismanagement of commingled groundwater-TTWW resources at all scales (national, catchment, metropolitan area, village, farm). © 2020 Desalination Publications. All rights reserved.