Modelling evaporative losses from the Darling River during drought using δ2H and δ18O

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Engineers Australia
The Darling River during drought has great pressure placed on it by extraction and impoundment of water during infrequent flow events throughout the catchment. Within the Darling River Basin evaporative losses can be extreme, contributing to the shortage of water in the system. Isotopic tracers can be used to assess water gains and losses and to separate evaporative losses from groundwater recharge or pumping. This study used ∼3 years of stable water isotope (δ2H and δ18O) data collected monthly at nine stations from Mungindi to Burtundy from 2002 to 2005 to determine the evaporative losses along the Barwon/Darling River. During extended dry periods evaporative enrichment of δ 2H and δ 18O is dramatic and using the Craig and Gordon (1965) model, as elucidated by Gonfiantini (1986), we modelled the fraction remaining after evaporation that is represented by the stable isotope composition of water along the river. This effectively represents a measure of evaporative losses undergone by water since its origin as precipitation within the catchment. Daily losses are commonly in the range of 0.1% to 1% of the original volume. The total level of evaporative loss commonly reached 40-60% between flow events in the upper reaches from Mungindi to Bourke, increasing downstream. Below the Menindee Lakes, evaporative losses were up to 80% due to the long period of impoundment of water in the Menindee Lakes system. © 2012 Engineers Australia.
Watersheds, Droughts, Ground water, Isotopes, Lakes, Groundwater recharge, Rivers, Runoff
Hughes, C. E., Hollins, S. E., Crawford, J., Meredith, K. T., & Cendón, D. I. (2012). Modelling evaporative losses from the Darling River during drought using δ2H and δ18O. In proceedings of the 34th Hydrology and Water Resources Symposium, Sydney; Australia; 19-22 November 2012, (pp. 423-428). Barton, ACT: Curren Associates Inc.