Impacts of groundwater extraction on salinization risk in a semi-arid floodplain

Abstract

Abstract. In the lower River Murray in Australia, a combination of a reduction in the frequency, duration and magnitude of natural floods, rising saline water tables in floodplains, and excessive evapotranspiration have led to an irrigationinduced groundwater mound forcing the naturally saline groundwater onto the floodplain. It is during the attenuation phase of floods that these large salt accumulations are likely to be mobilised and discharged into the river. This has been highlighted as the most significant risk in the MurrayDarling Basin and the South Australian Government and catchment management authorities have subsequently developed salt interception schemes (SIS). The aim of these schemes is to reduce the hydraulic gradient that drives the regional saline groundwater towards the River Murray. This paper investigates the interactions between a river (River Murray in South Australia) and a saline semi-arid floodplain (Clark's floodplain) that is significantly influenced by groundwater lowering due to a particular SIS. The results confirm that groundwater extraction maintains a lower water table and a higher amount of fresh river water flux to the saline floodplain aquifer. In terms of salinity, this may lead to less solute stored in the floodplain aquifer. This occurs through three mechanisms, namely extraction of the solute mass from the system, reducing the saline groundwater flux from the highland to the floodplain and changing the floodplain groundwater regime from a losing to a gaining one. It is shown that groundwater extraction is able to remove some of the solute stored in the unsaturated zone and this can mitigate the floodplain salinity risk. A conceptual model of the impact of groundwater extraction on floodplain salinization has been developed.

Optimizing the riparian zone width near a river for controlling lateral migration of irrigation water and solutes

“…For most sensitive model parameters including the saturated hydraulic conductivity (K s ), and the coefficients α and n of different soil layers were varied manually and no automated parameter optimization procedure was used to calibrate the model. In addition to a visual comparison of observed and simulated water table depths, a quantitative evaluation of the model performance was undertaken using goodness-of-fit measures (see Section 2.7) similar to other studies (e.g., Alaghmand et al, 2013Alaghmand et al, , 2014). The calibrated model was validated for 1461 days (1st July 2013 to 30th June 2017) by comparing the measured and simulated water table depths.…”

“…Similarly, Kidmose et al (2010) employed a conceptual groundwater flow and reactive transfer model to establish a relationship between flow paths and the fate of a pesticide in a riparian wetland. Alaghmand et al (2013) used a numerical model (Hydrogeosphere) to evaluate the interaction between a river and a saline floodplain in relation to groundwater fluctuations, incorporating evapotranspiration losses by riparian vegetation. Klatt et al (2017) explored the capability of a coupled hydro-biogeochemical model to evaluate the effectiveness of buffer strips to reduce nitrogen loads into aquatic systems.…”

Long-Term Impacts of Partial Afforestation on Water and Salt Dynamics of an Intermittent Catchment under Climate Change

“…Soil salinization, which affects large parts of land in arid and semi-arid climatic zones worldwide, is related to the accumulation of water-soluble salts near the ground surface that negatively affect vegetation, with consequent reductions in ecosystem and agricultural productivity [1][2][3]. Salinization often occurs in areas with shallow or rising groundwater tables that allow salt-rich water to interfere with the rooting zone to the possible detriment of the land cover [4,5].…”

Impacts of Vegetation Cover on Surface-Groundwater Flows and Solute Interactions in a Semi-Arid Saline Floodplain: A Case Study of the Lower Murray River, Australia

“…For instance, the EM31 survey in November 2007 displays a distinct zone of low conductivity along the eastern margin abutting the river channel (Berens et al 2009). A detailed description of the calibration process can be found in Alaghmand et al (2013a).…”

“…Transpiration from vegetation occurs within the root zone of the subsurface and is a function of the leaf area index (LAI), nodal water (moisture) content (θ) and a root distribution function (RDF) over a prescribed extinction depth (Alaghmand et al 2013a). Water content is simulated as saturation because it is more stable and always varies between 0 and 1, while in reality moisture content varies from 0 to a value equal to the porosity.…”