Using Desalinated Water for Irrigation: Its Effect on Field Scale Water Flow and Contaminant Transport under Cropped Conditions

Abstract

Pollution of groundwater by nitrate originating from irrigated fields was considered for this study. We hypothesized that under cropped conditions, low-salinity irrigation water (e.g., desalinated water) could reduce nitrate leaching below the root zone, due to two possible mechanisms: (i) decreased vertical water fluxes and (ii) increased nitrogen uptake by plant roots due to chloride-nitrate competition. The main goal of this study was to investigate this hypothesis. Considering a citrus grove, the investigation relied on three-dimensional (3-D) simulations of flow and transport in a variably saturated and spatially heterogeneous flow domain performed for three successive years. Results of the analyses suggest that the main mechanism responsible for the reduction in the nitrate leached below the root zone under irrigation with low-salinity water is the effect of the latter on the spatial distribution of the rate of water uptake by the roots. The latter, in turn, significantly reduces water content, hydraulic conductivity, and vertical velocity, and, consequently, solute mass fluxes along the soil profile. On the other hand, chloride-nitrate interaction has only a relatively small effect on the nitrate mass fluxes at relatively deep soil depths, far below the root zone, particularly when the irrigation water salinity decreases.Water 2019, 11, 687 2 of 17 managed aquifer recharge [11]; and, the most concerning, its use for irrigation. Unease has emerged due to the lack of the major nutrients, namely, calcium, magnesium, and sulfur, in desalinated seawater [12]. Half of the irrigation water in Israel is treated wastewater. The relatively low content of calcium and magnesium in desalinated water and the high addition of sodium in household use has raised concerns about the high sodium adsorption ratio (SAR) in wastewater originating from desalinated seawater [13].In contrast to the aforementioned concerns, the change towards lower salinity irrigation water may be regarded as an opportunity. Higher yields or smaller irrigation rates for the same yield and reduced leaching of salts below the roots are expected benefits of using more desalinated water for irrigation [14,15]. This study aims at showing that the use of low-salinity water for irrigation can also reduce the nitrate leaching to groundwater (the greatest groundwater pollution related to agriculture in Israel and worldwide, [16]). It is hypothesized here that under cropped conditions, low-salinity irrigation water may reduce nitrate leaching below the root zone, due to two mechanisms: (i) decreasing vertical water fluxes and (ii) increasing nitrogen uptake by plant roots when the latter process is affected by the competition between chloride and nitrate [17].The general objective of the present study was to investigate the effect of the irrigation water quality (salinity) on water uptake and nitrogen uptake by the plants' roots, and on the nitrate and the chloride mass fluxes below the root zone. Considering cropped conditions, the specific objective of this...

Characterization of the Agricultural Supply of Desalinated Seawater in Southeastern Spain

“…The total DSW supply for irrigation in 2017 was 148.3 Mm 3 in the SRB (9.6% of its total agricultural demand), and 29.0 Mm 3 in the AMB (5.9% of its total agricultural demand), which together amounted to 177.3 Mm 3 /year for SE Spain, a 66% of the maximum allocation intended for irrigation (77% when out of service SWDPs are not considered). This figure is similar to the agricultural supply of DSW in Israel during the period 2015-2017, which was estimated at 200 Mm 3 /year, about 40% of the national freshwater irrigation consumption [16]. Figure 3 presents the evolution of several water resources in the SRB, along with the agricultural DSW supply in the SRB and the AMB since 2005.…”

“…Moreover, the impact of the disposal of the elevated salinity brines on oceanic life and the risk to marine ecosystems of the release of chemicals used in desalination processes through the brine are also important general environmental concerns in seawater desalination [12,13]. Considering its pros and cons, the integration of DSW for agricultural use with traditional water sources would favor their economic viability, mitigate the agronomic risks and, ultimately, contribute to the sustainability of irrigation [14][15][16]. Moreover, agricultural DSW consolidation is expected in the coming years, with the advent of new technology and equipment that may reduce desalination costs [17].…”

How to Close the Gap of Desalinated Seawater for Agricultural Irrigation? Confronting Attitudes between Managers and Farmers in Alicante and Murcia (Spain)

“…Source: own elaboration from the questionnaires. Notes: 1 Petition was on 1986; 2 Latest statutes in 2015; 3 Although the first irrigation campaign with desalinated water was in 1979 with the arrival of the TST; 4 This surface increases until 3515 ha (taking into account the surface currently occupied by the industrial park); 5 This surface is reduced to 32,000 in a dry period; 6 Part of this surface (12,620 ha) corresponds to traditional irrigation (unregulated); 7 Some farms up to 200-300 ha; 8 Some farms up to 400 ha; 9 Some farms up to 40-50 ha; 10 Professional farmer: 20 ha, with 7-8 large fruit and vegetable companies (25-30 ha each one); 11 Some farms up to 50-100 ha; 12 One horticultural company uses 800 ha and a fruit company, about 300 ha; 13 Some horticultural companies up to 150 ha; 14 Vegetables include lettuce, broccoli, artichoke, cauliflower, tomatoes, celery, potato, onion, and pepper; while fruits include citrus, melon, watermelon, grape, and mango.…”

“…Furthermore, in the last six years, the world total water desalination capacity, including brackish water and seawater desalination, increased steadily with an annual rate of about 9% [11]. Likewise, the global production capacity of desalinated seawater is expected to double by 2040 [12].…”

Analysis and characterization of the use of non-conventional water sources for agricultural irrigation in the Segura basin

“…Teniendo en cuenta sus ventajas y sus desventajas, la integración de AMD en el uso agrícola con fuentes de agua tradicionales, favorecería su viabilidad económica, mitigaría los riesgos agronómicos y, en última instancia, contribuiría a la sostenibilidad de la agricultura de regadío (Russo et al, 2019). La previsión que hay para los próximos años es la de la consolidación del AMD como uno de los principales recursos hídricos para la agricultura de regadío en zonas costeras, potenciada además por la llegada de nuevas tecnologías que aportan una reducción de costes de producción y por tanto, abaratamiento en su uso generalizado (Burn,S.…”