Browsing by Author "Dawoud M"

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    Drainage, salt-leaching impacts, and the growth of Salicornia bigelovii irrigated with different saline waters
    (Elsevier B.V., 2023-09-14) Al-Tamimi M; Green S; Dahr WA; Al-Muaini A; Lyra D; Ammar K; Dawoud M; Kenyon P; Kemp P; Kennedy L; McLachlan A; Clothier B
    We sought to assess the impact on groundwater of using three types of saline waters to irrigate the halophyte Salicornia bigelovii Torrey in the hyper-arid United Arab Emirates. These were groundwater (GW) at 25 dS m−1, reverse-osmosis brine (RO) from a desalination unit at 40 dS m−1, and the aquabrine (AQ) effluent from land-based aquaculture in tanks filled with RO brine, also at 40 dS m−1. The three waters were applied through bubblers (BUB), pressure-compensated drippers (PCD), or subsurface irrigation tape (SUB). The yields of Salicornia fresh tips, harvest forage, and seed were greatest for AQ applied through BUB, being 650 g m−2. We found 2–2.6 kg m−2 for dry forage yield with AQ through BUB, compared with 1–2.3 kg m−2 for the other waters and emitter devices. The highest water productivities WPI (kg m−3) across all three crop-outputs came from Aquabrine applied by pressure-compensated drippers. We assessed the gross economic water productivity (GEWPI, $ m−3) based solely on gross revenue. The GEWPI was highest for AQ applied through PCD and SUB, namely 5.8–6.2 $ m−3. The value derives primarily from fresh tips. The GEWPl was well above the cost of desalination at $1.5 m−3. We measured drainage and leaching using fluxmeters. The greatest salt load to groundwater came from BUB, being 135–195 kg m−2. For PCD and SUB it was between 14 and 36 kg m−2. Mass-balance calculations of these salt loadings can predict the impact on the saline quality of aquifers. We used an exemplar loading of 75 kg m−2, and results in an annual salinity rise of 2.6 dS m−1 y−1 for an aquifer of saturated depth of 100 m. This significant rate of rise in the salinity of groundwater would represent a continuing deterioration in the utility of groundwater.
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    Measurement and heuristic modelling of nitrogen and salt dynamics under Salicornia growing in a hyper-arid region and irrigated with groundwaters of differing nutrient and Salt loadings
    (Springer Nature, 2024-10-03) Al-Tamimi M; Green S; Dahr WA; Al-Muaini A; Lyra D; Ammar K; Dawoud M; Kenyon P; Kemp P; Kennedy L; McLachlan A; Clothier B
    New data highlight the economic value of using nitrogen-rich saline waters, either from groundwater or reject brines from desalination units, to irrigate the halophytic crop Salicornia bigelovii for food, fodder, and fuel in a hyper-arid environment. The greatest benefit was achieved using pressure-compensated drippers. Field measurements of drainage and leaching under the crop showed that all of the salt and nitrogen from the groundwater was returned back to the aquifer as leachate. A simple, heuristic model of groundwater quantity and quality was developed to infer the environmental impacts of irrigating crops with saline and high-nitrate groundwater in a hyper-arid environment. The rise in solute concentration in groundwater is hyperbolic. The parameters needed for this simple model are the fraction of the land that is irrigated, the initial depth of the saturated thickness, the saturated water content, and the annual rate of evapotranspiration. An indicator of the time-rise is the number of years to double the solute concentration. This is ӨAho /2 ETC, where ӨA is the aquifer’s saturated water content, ho is the original thickness of the saturated layer, and ETc is the annual rate of crop evapotranspiration. The general model is simple and straightforward to parameterise to predict the evapoconcentration of groundwater salinity.
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    Salt dynamics, leaching requirements, and leaching fractions during irrigation of a halophyte with different saline waters
    (CSIRO Publishing, 2023-12-18) Al-Tamimi M; Green S; Dahr WA; Al-Muaini A; Lyra D; Ammar K; Dawoud M; Kenyon P; Kemp P; Kennedy L; Clothier B; McGrath G
    Context More than 830 million ha of soils are salt affected, representing around 9% of the world’s land surface. Groundwater high in salt already covers some 16% of the land area. Saline water can be used effectively for irrigation by salt leaching to despatch the accumulated salts, but this can pose a risk of salinisation of groundwater. It is important that the efficacy of salt leaching is confirmed, and the impacts of salt loading below the rootzone can be assessed. Aims We examine the efficiency and impact of salt leaching to remove salt from the rootzone. Methods Our soil, a Typic Torripsamment, is the dominant soil across the Arabian Peninsula. We carried out detailed laboratory experiments of salt leaching dynamics via salt breakthrough curves, analytical modelling, and through the field monitoring of impacts. Key results Analytical solutions well predicted the salt breakthrough curves from repacked soil columns in the laboratory and we were able to confirm that all of the soil’s water was actively involved in transport, and that salt behaved as an inert tracer. The breakthrough curves were well predicted using a small solute dispersivity, so piston displacement was found to be a good assumption. Salt was easily flushed from the columns. To back this up in the field, soil sampling was carried out down to 1 m across 36 profiles after the harvest of a halophytic crop irrigated with saline water. Salt storage was only 1.8 kg m−2, even though 80 kg m−2 had been applied. This is a positive result for managing irrigation. Conclusions Salt leaching can maintain equable salinity in the rootzone. However, this leaching carried salt back to groundwater at 2–3 times the concentration of the applied water. We confirmed that the amount of salt leaching back to groundwater can be significant. Implications This salt dilemma will require careful management to achieve crop yields and protect the environment.