Understanding salt mobilization from an irrigated catchment in south‐eastern Australia

Abstract

Abstract:Groundwater discharge from the Riverine Plains of the southern Murray-Darling Basin is a major process contributing salt to the Murray River in Australia. In this study, data from an irrigated 60 000 ha catchment in the Riverine Plains were analysed to understand groundwater discharge into deeply incised drains, the process dominating salt mobilization from the catchment. We applied three integrated methodologies: classification and regression trees (CART), conceptual modelling and artificial neural networks (ANNs) to a comprehensive, spatially lumped, monthly data set from July 1975 to December 2004. Using CART analysis, it was shown that rainfall was the most important variable consistently explaining the salt load patterns at the catchment outlet. Using the conceptual model representing spatially lumped groundwater discharge into deeply incised drains, we demonstrated that salt mobilization from the study catchment can be well represented by a rainfall contribution, influenced by the hydraulic head in the deep regional aquifer and potential evapotranspiration. Using ANNs, it was confirmed that rainfall had a much higher impact on salt loads at the catchment outlet than irrigation water use. All these results demonstrate that under conditions similar to those experienced from 1975 to 2004, it is rainfall rather than irrigation water use that governs salt mobilization from the study catchment. Management of salt mobilization from irrigated catchments has traditionally focussed on the improvement of irrigation practices but it could be equally important to further understand the scope for management to control groundwater discharge in these irrigation areas.

Recharge estimation using remotely sensed evapotranspiration in an irrigated catchment in southeast Australia

“…Since the mid 90s, the water table in the shallow aquifer has fallen slightly while hydraulic heads in the deeper aquifer have shown a marked decline (Selle et al , 2010). Further, most of the drains did not intercept groundwater flow as was previously the case.…”

“…The estimated recharge for the season 2002/2003 was substantial and on average represented about 40% of the total rainfall and irrigation inputs. In contrast, recharge during wetter years (1976–1995) estimated at a lumped catchment scale was about 3% of both rainfall and irrigation (Selle et al , 2010). Note that the rainfall in the wetter years was almost twice that in 2002/2003.…”

“…The measured annual water delivery for the study area was strongly correlated with water delivered through Channel No. 1, with the channel accounting for 60% of the total irrigation water use in the catchment (Selle et al , 2010). The daily water use for the catchment was then calculated as Channel No.…”

The Importance of Spatiotemporal Variability in Irrigation Inputs for Hydrological Modeling of Irrigated Catchments

“…1 Channel (see Figure ). Selle et al () found that the measured annual water supply into the Barr Creek catchment was strongly correlated with the annual water supply through the channel offtake, with water delivered through the channel accounting for 60% of the total irrigation water use in the catchment (with the remaining 40% supplied through other channels). This correlation was used to estimate daily catchment irrigation for the entire catchment from the daily data for the No.…”

Spatio-Temporal Patterns of Water Table and Vegetation Status of a Deserted Area

“…However, such an understanding has been greatly limited by scarce data, which makes it impossible to use advanced spatial statistical methods (e.g., geostatistical analysis and multivariate regression) [37,38]. The objectives of this study were therefore to conduct an exploratory analysis to examine: (1) spatio-temporal variations in the water table beneath a selected area within the HSL; and (2) the relationship between variations in the depth of the water table and the overall vegetation status of the selected area.…”