Agricultural Groundwater Use Research Articles

Investigation of Salt Tolerance Mechanisms Across a Root Developmental Gradient in Almond Rootstocks.

The intensive use of groundwater in agriculture under the current climate conditions leads to acceleration of soil salinization. Given that almond is a salt-sensitive crop, selection of salt-tolerant rootstocks can help maintain productivity under salinity stress. Selection for tolerant rootstocks at an early growth stage can reduce the investment of time and resources. However, salinity-sensitive markers and salinity tolerance mechanisms of almond species to assist this selection process are largely unknown. We established a microscopy-based approach to investigate mechanisms of stress tolerance in and identified cellular, root anatomical, and molecular traits associated with rootstocks exhibiting salt tolerance. We characterized three almond rootstocks: Empyrean-1 (E1), Controller-5 (C5), and Krymsk-86 (K86). Based on cellular and molecular evidence, our results show that E1 has a higher capacity for salt exclusion by a combination of upregulating ion transporter expression and enhanced deposition of suberin and lignin in the root apoplastic barriers, exodermis, and endodermis, in response to salt stress. Expression analyses revealed differential regulation of cation transporters, stress signaling, and biopolymer synthesis genes in the different rootstocks. This foundational study reveals the mechanisms of salinity tolerance in almond rootstocks from cellular and structural perspectives across a root developmental gradient and provides insights for future screens targeting stress response.

Hydrochemical characterization and quality assessment of groundwater in Meki River Basin, Ethiopian Rift

The present study was carried out in Meki River Basin (Ethiopian Rift) aiming at characterizing the hydrochemical composition of groundwater and evaluating the water quality status for drinking and irrigation uses. For this purpose, 63 primary groundwater samples from springs, hand-dug wells, and boreholes were collected and subjected to major ions analysis besides the in situ tests. The analysis result illustrates that Na+ and HCO3− are the principal cation and anion in the study area. The spatial investigation of the physiochemical parameters revealed that temperature, pH, TDS, EC, Na+, K+, HCO3−, Cl−, SO42−, and F− show a positive trend from the highland towards the rift floor along the groundwater flow direction. On the contrary, Ca2+ and Mg2+ show a negative tendency along the groundwater flow path. The groundwater of the study area generally evolves from predominantly fresh (TDS 750 mg/l) Na–HCO3 water type in the rift floor following the regional groundwater flow path. Gibbs diagram supported by ionic ratio (Na+ + K+/Ca2+ + Mg2+ vs total cations (TZ+) and Chloro-Alkaline Indices (CAIs) suggests that rock–water interaction (silicate hydrolysis and cation exchange) is the major hydrochemical processes controlling the evolution of the groundwater in the study area. 19% of TDS, 11% of EC, 83% of K+, 84% of HCO3−, and 52% of F− of the total water samples were unsuitable for the drinking uses compared with WHO water quality guideline. Spatial distribution maps of major ions (Ca2+, Mg2+, Na+, K+, Cl−, HCO3−, SO42−, and F−) and binary plots of physical parameters (temperature, pH, TDS, and EC) with elevation were produced. Both the spatial maps and binary plots generally show a water quality drop rift wards. Similarly, using multiple agriculture water quality criteria such as EC, SAR, RSC, PI, and Na%, the suitability of the groundwater for agricultural use was evaluated. Except a few samples in the rift floor, the majority of the water samples are found to be suitable for irrigation uses. As the study area is located where active geothermal activity and fluid circulation through fault systems, it is highly advised to carry out further toxic trace elements analysis to investigate the possible influence on the water quality.

Farmer Behavior Under Groundwater Management Scenarios: Implications for Groundwater Conservation in the Mississippi Alluvial Plain

Concern about sustained availability of fresh groundwater for agricultural use in the Mississippi Alluvial Plain (MAP) mounts as groundwater levels decline. We evaluate the elasticities of demand for groundwater and other agricultural inputs, as well as the overall and output-specific economies of scale for four major irrigated commodities (rice, corn, soybeans, and cotton) in the MAP region. Additionally, we investigate the impacts of two groundwater management policy scenarios, including increasing pumping cost and groundwater use restrictions, on irrigation behavior. The results show price elasticity of demand for groundwater to be [Formula: see text], indicating that it is inelastic, and an increased cost of pumping will not significantly decrease the relative demand for groundwater in the region. Even with policy scenarios that either increase the costs of pumping significantly or restrict groundwater use in the region, groundwater demand still appears to be inelastic. We also document significant overall economies of scale in the region. Our findings have implications for potential policy options aimed at reducing groundwater use. Efficient management practices are important to increase aquifer recharge, and considering human behavior via economic analysis will improve projections of groundwater availability in the MAP region.

Fine-scale spatiotemporal variation in subsidence across California’s San Joaquin Valley explained by groundwater demand

Achieving sustainable agricultural groundwater use remains a significant challenge worldwide in part because data on groundwater withdrawals are limited. A new generation of interferometric synthetic aperture radar (InSAR) data provide high spatial- and temporal- resolution measurements of subsidence and uplift of the earth’s surface, which are known to reflect change in groundwater storage below. Here, we establish for the first time a quantitative link between local irrigation water demand and InSAR-derived vertical land surface displacements in California’s San Joaquin Valley, with the goal of increasing the utility of remotely sensed displacements for understanding and managing groundwater at fine scales. We relate 100 m, sub-monthly displacements to estimates of irrigation water demand generated from land cover and weather data by performing a suite of physical process-motivated statistical analyses that leverage (i) temporal variations in surface water supplies created by climate, and (ii) spatial variations in water demand created by different land uses. Between 2015 and 2017, cultivated land experienced up to seven times the total subsidence, and up to nine times the dry year subsidence rate, of uncultivated land. In uncultivated areas, subsidence rates differed minimally across dry and wet years. In contrast, within cultivated areas, dry year subsidence rates were more than double wet year rates, indicating increased agricultural groundwater pumping under diminished precipitation and surface water supplies. Mean subsidence, and the marginal response of subsidence to water demand, were greatest for cultivated lands and for field and pasture crops in particular, and were also proportional to distance from surface water supply infrastructure. These findings demonstrate that land surface observations have the potential for use in the quantification of connected surface water and groundwater processes at policy-relevant scales.

Trade-offs across the water-energy-food nexus: A triple bottom line sustainability assessment of desalination for agriculture in the San quintín Valley, Mexico

This paper introduces a novel triple bottom line sustainability assessment to evaluate the water-energy-food nexus of desalination for agriculture. Falling technology costs and rising water scarcity worldwide make desalination an increasingly attractive proposition, and agriculture is one of the main sectors grappling with its potential impacts. To explore this issue, we combine a wide range of primary and secondary environmental, economic, and social data with a triple bottom line / WEF nexus analysis, to demonstrate both the holistic sustainability impacts of desalination for agriculture, and the multi-sectoral policy environment within which desalination is adopted. We apply this approach to 54 privately-owned desalination plants that treat brackish groundwater for agricultural use in the San Quintín Valley of Baja California, Mexico. We find that subsidized energy for local agribusinesses plays an important role in making desalination economically viable in the region. This in turn fuels a large agricultural export industry that represents a significant virtual water transfer to the US market. Rapid population growth in the area driven by agricultural labor needs exacerbates the issues of social equity and sustainability that these subsidies and transfers raise. We conclude with a discussion of how to manage these identified trade-offs across the water-energy-food nexus.

Rationing the Commons

Common resources may be managed with inefficient policies for the sake of equity. We study how rationing the commons shapes the efficiency and equity of resource use, in the context of agricultural groundwater use in Rajasthan, India. We find that rationing binds on input use, such that farmers, despite trivial prices for water extraction, use roughly the socially optimal amount of water on average. The rationing regime is still grossly inefficient, because it misallocates water across farmers, lowering productivity. Pigouvian reform would increase agricultural surplus by 12% of household income, yet fall well short of a Pareto improvement over rationing. Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at www.nber.org.

Desertifying deserts

The current definition of desertification excludes hyper-arid zones given their lack of economic activity. However, the 101 million people living there, ongoing land degradation associated with the use of groundwater for intensive agriculture and climate-change-induced aridity call for a revision of this definition.

Delineating groundwater potential zones of agriculture dominated landscapes using GIS based AHP techniques: a case study from Uttar Dinajpur district, West Bengal

Groundwater depletion and contamination has increased in recent decades due to increased groundwater use and the intensification of agricultural practices. The increasing demand for groundwater has increased the need to identify areas in a landscape where groundwater resources are most likely to be available. The present study was conducted on three management blocks in West Bengal in India where excessive groundwater use for agriculture primarily has caused groundwater levels to decrease. An AHP technique was employed to compile a groundwater resources potential map for the study area. The map was compiled using ten thematic layers including: geomorphology, slope, geology, landuse/landcover, rainfall, slope curvature, the Modified Normalized Difference Water Index, drainage density, soil type and the Topographic Wetness Index. The groundwater potential map has been validated using the groundwater fluctuation data and correlated with agricultural dependency on groundwater. The final potential map obtained categorized the regions into five categories. These are areas with a poor, low, moderate, high and very high prospectivity.

Spatial variation of groundwater quality and assessment of water table fluctuations in Plio-Quaternary aquifer formations in Doukkala Plain, Morocco

Groundwater quality and water table fluctuation baseline study were carried out along Doukkala Plain, one of largest agricultural regions in Morocco, bringing together and comparing information from 1995s to 2016s analysis. The depths of wells, the pH, electrical conductivity, and temperature of groundwater were measured in situ for 160 groundwater samples in May 2016. The study of water table fluctuation between 1995 and 2016 showed a continuous rise of the piezometric level from 0.7 to 0.8 m/year in large irrigation schemes. While in the rainfed agriculture area the piezometric level was decreased from 5 to 10 m. The obtained results showed that the level of water table was affected by seasonal variations in consequence to rainfall, irrigation water, and groundwater over-pumping. Groundwater chemistry was also carried out in this research using laboratory analyses of major cations Na+, K+, Ca2+, and Mg2+ and anions Cl−, HCO3−, NO3− and SO42−. Electrical conductivity, nitrate levels, and total hardness were used as indicators to determine groundwater quality and suitability for drinking purposes. The values of these indicators were ranged from 640 to 11950 μS/cm, 0–152.10 mg/L, and from 149.2 to 2081.6 mg/L, respectively. While the suitability of groundwater for agricultural use was determined using sodium adsorption ratio (SAR) and sodium percentage (Na%). SAR values ranged from 1.96 to 17.96 meq/L and sodium percentage values ranged from 22.28 to 86.09%. These results showed that the chemical composition of groundwater fell above acceptable limits recommended by WHO (2011) for drinking water suitability. In contrast, groundwater is suitable for agriculture use at most locations. The unconfined Doukkala Aquifer is under stress due to the impact of anthropogenic activities and climate change. Therefore, widely sharing these results will enable farmers, public and government departments to adopt sustainable solutions for the management of Doukkala Aquifer.

INNOVATIONS IN IRRIGATION SYSTEMS IN AFRICA†

INNOVATIONS IN IRRIGATION SYSTEMS IN AFRICA^†

Rationing the Commons

Common resources may be managed with inefficient policies for the sake of equity. We study how rationing the commons shapes the efficiency and equity of resource use, in the context of agricultural groundwater use in Rajasthan, India. We find that rationing binds on input use, such that farmers, despite trivial prices for water extraction, use roughly the socially optimal amount of water on average. The rationing regime is still grossly inefficient, because it misallocates water across farmers, lowering productivity. Pigouvian reform would increase agricultural surplus by 12% of household income, yet fall well short of a Pareto improvement over rationing.

An assessment of groundwater use in irrigated agriculture using multi-spectral remote sensing

Declining water resources in dry regions requires sustainable groundwater management as trends indicate increasing groundwater use, but without accountability. The sustainability of groundwater is uncertain, as little is known about its extent and availability, a challenge that requires a quantitative assessment of its current use. This study assessed groundwater use for irrigated agriculture in the Venda-Gazankulu area of Limpopo Province in South Africa using crop evapotranspiration and irrigated crop area derived from the normalised difference vegetation index (NDVI). Evapotranspiration data was derived from the Water Productivity through Open access of Remotely sensed Actual Evapotranspiration and Interception (WaPOR) dataset (250 m resolution), and irrigated areas were characterised using dry season NDVI data derived from Landsat 8. Field surveys were conducted for four years to assess accuracy and for post-classification correction. Daily ET for the dry season (May to September) was developed from the actual ET for the irrigated areas. The irrigated areas were overlaid on the ET map to calculate ET for only irrigated land parcels. Groundwater use during the 2015 dry period was 3627.49 billion m3 and the irrigated area during the same period was 26% of cultivated land. About 82 435 ha of cultivated area was irrigated using 44 million m3/ha of water, compared to 186.93 million m3/ha on a rainfed area of 237 847 ha. Groundwater management is essential for enhancing resilience in arid regions in the advent of water scarcity.

Can shallow groundwater sustain small-scale irrigated agriculture in sub-Saharan Africa? Evidence from N-W Ethiopia

We present an evidence-based approach to identify how best to support development of groundwater for small-scale irrigation in sub-Saharan Africa (SSA). We argue that it is important to focus this effort on shallow groundwater resources. We demonstrate and test this proposal at a case study site: Dangila woreda in the north-western highlands of Ethiopia. This site was selected to allow exploration of a shallow weathered volcanic regolith type aquifer formation which is found to the South of Lake Tana and also exists more extensively across Ethiopia. We believe lessons from this case study are transferable and there is a case for arguing that shallow groundwater represents a neglected opportunity for promoting sustainable small-scale irrigated agriculture in SSA.In comparison with other global regions, the groundwater resources of SSA are among the least understood; borehole records and hydrogeological studies are lacking. Assessments of groundwater resources do exist, but they rely on remotely sensed data combined with modelling at national or regional scale, and they focus on deeper aquifers. There is a need for these broad evaluations to be supplemented by localised and detailed assessments. The case study here presents such an assessment in order to support analysis of strengths, weaknesses, opportunities and threats associated with developing small-scale irrigation utilising shallow groundwater.A multimethod groundwater recharge assessment was conducted utilising formal and community-based monitoring, field investigation and existing published data. Water table recovery tests at existing hand dug wells confirm that well yields of 1 l/s are achievable at the end of the wet season when water would be available to support an additional irrigated crop. Hydraulic conductivity estimates ranged from 0.2 to 6.4 m/d in the dry season and from 2.8 to 22.3 m/day in the wet season. Specific yield estimations have a wider range though the mean value of 0.09 is as would be expected.Records of groundwater levels and rainfall monitored by the local community for the period April 2014 to April 2018 show that all the wells maintained useable water levels beyond the end of the rainy season. An assessment of the hydrology of the Kilti catchment provided insights into groundwater availability within the wider area. The catchment receives about 1600 mm/year of rainfall, of which about 350 mm/year enters the groundwater as recharge, discharging to the river as baseflow with a similar amount of rapid runoff contributing to a total river flow of about 400 mm/year. The lowest value of baseflow is 82% of the mean baseflow, which suggests a degree of buffering and indicates that groundwater is available even in a very dry year.We conclude that arguments previously put forward against the promotion of shallow groundwater use for agriculture in SSA appear exaggerated. Our analysis challenges the view that shallow aquifers are unproductive and that irrigation will have unacceptable impacts on wetlands and other groundwater-dependent ecosystems. We believe lessons from this case study are transferable, and there is a case for arguing that shallow groundwater represents a neglected opportunity for promoting sustainable small-scale irrigated agriculture in sub-Saharan Africa. It appears that factors other than the physical availability of groundwater control the ‘triggering’ of development. Interventions to promote development of groundwater resources should recognise the importance of shallow aquifers.

Groundwater governance: Addressing core concepts and challenges

AbstractWith decreasing aquifer levels, increasing groundwater pollution, inequitable access, and generally poor management outcomes, better groundwater governance has been put forward as a recipe to address these challenges worldwide. Existing recommendations focus on improved legal frameworks, monitoring and control of access and abstraction through permits or formal rights. In addition, decentralized water management, enforcement of regulations, and supply‐side technological solutions are seen as cornerstone components of good groundwater governance systems. However, until now, these approaches have generally failed to reconcile the fundamental dynamics and properties of groundwater as a natural resource and of governance as a social and political phenomenon. This has caused a disregard for local to planetary boundaries, power dynamics, and intra‐ and intergenerational inequalities in access to benefits from groundwater. As the current general notion of good groundwater governance is limited, solutions put forward are also partial and do not encompass the wider challenges affecting groundwater governance, in effect replacing sustainable management goals and policy for governance as a process. This paper takes a particular look at the Middle East and North Africa and agricultural groundwater use for irrigation to constructively redefine groundwater governance and fully address the multilayered and multifaceted core challenges of groundwater governance. Equally, the paper puts forward a new conceptual thinking that will help support the effective development of governance‐based solutions to achieve sustainable, socially acceptable, resilient and equitable resource use.This article is categorized under: Engineering Water > Planning Water Human Water > Water Governance

Integrated hydrogeological modelling of hard-rock semi-arid terrain: supporting sustainable agricultural groundwater use in Hout catchment, Limpopo Province, South Africa

An integrated hydrogeological modelling approach applicable to hard-rock aquifers in semi-arid data-scarce Africa was developed using remote sensing, rainfall-runoff modelling, and a three-dimensional (3D) dynamic model. The integrated modelling approach was applied to the Hout catchment, Limpopo Province, South Africa, an important agricultural region where groundwater abstraction for irrigation doubled during 1968–1986. Since the 1960s, groundwater levels in irrigated areas have displayed extended periods of decline with partial or full recovery in response to major decadal rainfall events or periods. The integrated dynamic 3D hydrogeological flow model, based on the One-Water Hydrologic Flow Model (MODFLOW-OWHM), helped to understand recharge and flow processes and inform water use and management. Irrigation abstraction was estimated based on irrigated crop area delineated using the Landsat Normalized Difference Vegetation Index (NDVI) and crop water requirements. Using groundwater level data, the model was calibrated (2008–2012) and validated (2013–2015). Estimated mean diffuse recharge (3.3 ± 2.5% of annual rainfall) compared well with estimates from the Precipitation Runoff Modelling System model. Recharge and groundwater storage showed significant inter-annual variability. The ephemeral river was found to be losing, with mean net flux to the aquifer (focused recharge) of ~1.1% of annual rainfall. The results indicate a delicate human-natural system reliant on the small but highly variable recharge, propagating through variable pumping to an even more variable storage, making the combined system vulnerable to climate and anthropogenic changes. The integrated modelling is fundamental for understanding spatio-temporal variability in key parameters required for managing the groundwater resource sustainably.

Putting farmers’ strategies in the centre of agricultural groundwater use in the Vientiane Plain, Laos

ABSTRACT Groundwater use for agriculture has the potential to improve rural households’ income and reduce poverty, but the linkages are not always straightforward. Taking Laos as a case study, this article illustrates how differential access to water, land, and capital shape farmers’ livelihood strategies in two nearby, yet contrasting villages on the Vientiane Plain. It examines the factors driving farm households’ decisions to invest in groundwater for agriculture. The findings highlight the need to better understand how farmers view groundwater in relation to their farm household characteristics if groundwater is to be successfully used as a means to improve rural livelihoods.

Irrigation management with saline groundwater of a date palm cultivar in the hyper-arid United Arab Emirates

The United Arab Emirates has a hyper-arid climate. Irrigation is essential for dates (Phoenix dactylifera L.), an important crop economically and culturally. Groundwater is relied on, yet it is a non-renewable resource at the rate it is being used. Furthermore, as the water-table drops, it is becoming more saline. Law no. 5 has been passed in Abu Dhabi to regulate the use of groundwater and set allocation limits for agriculture. For assessing the allocation of irrigation water to date farms under Law 5, we carried out measurements of tree water-use by the compensation heat-pulse method, complemented by measurements of the changing soil-water dynamics using time domain reflectometry and bulk soil electrical conductivity. Over four years we measured the hourly pattern of Lulu date-palm water use, ETc, at two levels of irrigation-water salinity: Treatment S1 at 5 dS m−1, and S3 at 15 dS m−1. The mid-summer ETc for the S1 Lulu trees is up to 190 L d−1, on average, whereas for the S3 trees ETc is lower at 130 L d−1 (68% of S1) because of the salt. Measurements of canopy radiation interception using a ‘light stick’ showed the S1 trees intercepted 26% of the incident radiation, whereas the S3 trees only intercepted 20% (ratio S3/S1 = 76%). The date yield of the S1 trees was 68 kg tree−1, but was 46 kg tree−1 for the S3 trees (ratio 68%). Current practice is to irrigate trees with 275 L d−1, irrespective of salinity. Our recommendation for Law 5 is to tailor irrigation to the seasonal demand in the reference evapotranspiration of ETo, and allow for a 25% factor-of-safety and a 25% salt leaching fraction. For S1 date palms this would mean an annual average of 210 L d−1, and for S3 just 137 L d−1. This represents savings of 25–50% from current practice.

Limitations of GALDIT to map seawater intrusion vulnerability in a highly touristic coastal area

Coastal aquifers are susceptible to seawater intrusion, especially touristic areas where the overexploitation combined with the agricultural use of groundwater represent a severe issue for water management. GALDIT methodology was applied as a management tool to identify and prevent salinization of the aquifer. GALDIT methodology needs six input parameters: groundwater occurrence (G), aquifer hydraulic conductivity (A), groundwater head above sea level (L), distance from the shore (D), impact of the existing status of seawater intrusion (I), and thickness of the aquifer (T). Then a contour map is created using three degree of vulnerability: high, medium and low. The higher vulnerability zone ranges from 40 to 550 m towards the mainland with the rest of the aquifer characterized by medium vulnerability. The main problem affecting the selected field site is the large water requirement during the summer period due to the touristic activities, but the correct use of surplus water collected in the winter can overcome this problem. This study demonstrates that further investigation on groundwater hydrochemistry and on water demand trends from the different activities impacting the field site should be implemented, in order to guarantee environmental and touristic development sustainability.

Jevons’ Paradox and Efficient Irrigation Technology

Water is one of our world’s most essential natural resources, but it is also a resource that is becoming increasingly scarce. The agricultural use of groundwater is particularly important to manage sustainably and well. However, popular and well-intentioned water conservation and management policies, including those that encourage the adoption of more efficient irrigation technology, may have unintended and possibly perverse consequences if policy-makers do not account for water users’ behavioral responses to their policies. In particular, a Jevons’ Paradox may arise, whereby a technology that enhances the efficiency of using a natural resource does not necessarily lead to less consumption of that resource. In this paper, we discuss efficient irrigation technology, Jevons’ Paradox, and the possible perverse consequences of incentive-based programs for agricultural groundwater conservation.

Groundwater chemical indices changed due to water-level decline, Minab Plain, Iran

This study tried to investigate the change in the physical and chemical indices of groundwater in Minab Plain caused by groundwater level decline. In this regard, twelve groundwater samples were drawn from different wells across this plain during 22 November to 22 December 2015. The parameters of acidity, electrical conductivity (EC), and temperature and the major anions and cations were measured in situ and at the regional water laboratory of Hormozgan, respectively. Comparison of the current parameters with EC and chloride Cl−, and the measured parameters during 2006 indicated an increased concentration of EC, Cl−, sodium Na+, bicarbonates HCO3, total dissolved solids TDS, as well as total hardness TH, and a decreased concentration of sulphate SO42− over time. According to the findings in a lower groundwater quality and a higher groundwater salinity, groundwater level and reservoir capacity decreased by 11.3 m and 287.2 million m3, respectively; finally, for quality assessment of the region’s groundwater for agricultural use, values of sodium absorption ratio, sodium percentage (Na%), residual sodium carbonate, and magnesium hazard were computed; comparison of the concentrations of major cations and anions in the regional groundwater showed that the dominant cationic and anionic conditions were Na > Mg > Ca > K and Cl > HCO3 > SO4 > CO3, respectively. Comparison of the measured parameters with Iran’s national standard and the World Health Organization standards showed that the pH and calcium Ca2+ values of all samples were at desirable levels. Results suggested that the regional waters had good, acceptable, and average quality for drinking. In terms of agricultural use, the dominant cations in the regional groundwater were Na+, followed by magnesium Mg2+.