US EPA

3332702 

Journal Article 

Hydro-ecological modelling to establish sustainable extraction limits in unregulated catchments 

Savadamuthu, K; van Der Wielen, M; Alcorn, MR; Vanlaarhoven, J 

2011 

4113-4119 

WOS:000314989304012 

Statutory water allocation plans are an important tool for sustainable water resource management in South Australia. Water allocation plans need to achieve a balance between social, economic and environmental needs for water when establishing sustainable extraction limits. This paper outlines the hydrological and ecological modelling interface used in helping to develop the proposed sustainable extraction limits for the surface water resources of the Mt Lofty Ranges (MLR) region. Two draft water allocation plans have been recently prepared, one for the eastern MLR and one for the western MLR. The catchments are ephemeral and largely unregulated, where the majority of surface water capture is via thousands of private farm dams. The larger catchments in the western MLR also include public water-supply reservoirs supplying Adelaide. A key challenge is to develop sustainable extraction limits and taking rules, which will practically apply to thousands of private dams in order to provide an environmentally appropriate water regime, as well as providing for social and economic water needs. In developing the plans, key components that contributed to defining sustainable extraction limits included: Surface water resource capacity - Catchment modelling to estimate the total quantity of water available within the MLR region (daily and annual flow), with the impact of recent developments (farm dams, plantation forestry and watercourse extractions) accounted for. Environmental water requirements (EWR) - Representation of EWRs as a series of hydrological statistics, termed as 'EWR metrics'. An environmental target was set, based on the metrics, which was expected to have an acceptable level of risk of meeting the environmental objectives. Scenario modelling - Scenario modelling was used to estimate impacts of different management strategies on meeting the environmental target and consumptive demands across the MLR, including current conditions, variable demand, and taking rules that return low flows to the environment. The outcomes were used to assist identifying sustainable extraction limits that balance different water needs. A suite of hydrological and ecological modelling tools were used, including: Water resource modelling platform (WaterCress) to represent the various water supply and demand components of the water-balance. Rainfall-runoff models within the modelling platform. Daily time-step partially distributed catchment models were calibrated for all the long-term gauged sub-catchments in the region. Rainfall-runoff relationships developed from these calibrated models were then used to simulate runoff from similar neighboring ungauged sub-catchments. Rainfall, slope, soil type and land cover parameters were used to extend the rainfall-runoff relationships to ungauged catchments. An analysis framework to link various components of the water balance and flow model outputs to EWR metrics. This enabled simulation of various demand scenarios and their impacts on the flow regime. The above-mentioned suite of hydro-ecological modelling and analysis tools were then linked to derive the final sustainable extraction limits (SEL) for the entire MLR region. 

Water allocation planning; modelling; hydrology; hydrological modelling; hydro-ecological modelling; environmental water requirements; environmental water provisions; sustainable extraction limits; catchment water-balance; rainfall-runoff generation