Ecohydrological and socioeconomic integration for the operational management of environmental flows

Abstract

Abstract. Investment in and operation of flow control infrastructure such as dams, weirs, and regulators can help increase both the health of regulated river ecosystems and the social values derived from them. This requires high-quality and high-resolution spatiotemporal ecohydrological and socioeconomic information. We developed such an information base for integrated environmental flow management in the River Murray in South Australia (SA). A hydrological model was used to identify spatiotemporal inundation dynamics. River ecosystems were classified and mapped as ecohydrological units. Ecological response models were developed to link three aspects of environmental flows (flood duration, timing, and interflood period) to the health responses of 16 ecological components at various life stages. Potential infrastructure investments (flow control regulators and irrigation pump relocation) were located by interpreting LiDAR elevation data, digital orthophotography, and wetland mapping information; and infrastructure costs were quantified using engineering cost models. Social values were quantified at a coarse scale as total economic value based on a national survey of willingness-to-pay for four key ecological assets; and at a local scale using mapped ecosystem service values. This information was integrated using a constrained, nonlinear, mixed-integer, compromise programming optimization model and solved using a stochastic Tabu search algorithm. We tested the model uncertainty and sensitivity using 390 Monte Carlo model runs at varying weights of ecological health vs. social values. Integrating ecohydrological and socioeconomic information identified environmental flow management regimes that efficiently achieved both ecological and social objectives. Using an ecologically weighted efficient and socially weighted efficient scenario, we illustrated model outputs including a suite of cost-effective infrastructure investments and an operational plan for new and existing flow control structures including dam releases, weir height manipulation, and regulator operation on a monthly time step. Both the investments and management regimes differed substantially between the two scenarios, suggesting that the choice of weightings on ecological and social objectives is important. This demonstrates the benefit of integrating highquality and high-resolution spatiotemporal ecohydrological and socioeconomic information for guiding the investment in and operational management of environmental flows.

Quantifying Tradeoffs Associated with Hydrologic Environmental Flow Methods

“…Comparisons between environmental flow methods also showed the importance of stakeholder preferences in recommending a flow regime (Poff et al ., ; Arthington, ; Bryan et al ., ; Pahl‐Wostl et al ., ). Tradeoffs were shown both within a single method (e.g., multiple minimum flow thresholds, Figure ) and across methods (e.g., UMFs v .…”

“…Conversely, if a user wished to only maximize hydrologic similarity to the unaltered hydrograph, then w w = 0 and w r = 1. Rather than imposing a value judgment, a range of weights ( w w = 0.00, 0.01,…, 1.00) was applied to examine sensitivity of decision making to values (Bryan et al ., ).where U is the overall utility of an environmental flow scenario.…”

“…These techniques are often placed into four categories (Jowett, ; Tharme, ; Acreman and Dunbar, ; Arthington et al ., ): hydrologic methods, hydraulic rating, habitat analysis, and holistic methodologies. However, recent environmental flow analyses are also utilizing optimization methods (e.g., Harman and Stewardson, ; Suen and Eheart, ; Yin et al ., ; Bryan et al ., ) and regionalization approaches (e.g., Poff et al ., ; Sanderson et al ., ; Snelder et al ., ; Kendy et al ., ) as tools for identifying environmental flow recommendations (McKay, ).…”

“…As declared by more than 750 scientists from 50 countries in the Brisbane Declaration (2007), "Environmental flows describe the quantity, timing, and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and well-being that depend on these ecosystems." At the crux of this definition is the balance of water provision between ecological and human needs, which can be synonymous (Baron et al, 2002;Richter, 2010;Bryan et al, 2013). However, river flow regimes exhibit numerous sources of variability relative to the magnitude, frequency, timing, duration, and rate-ofchange of river discharge or stage (Poff et al, 1997), which can result in numerous effects on ecological processes (Bunn and Arthington, 2002;Arthington, 2012).…”

Challenges in Using Hydrology and Water Quality Models for Assessing Freshwater Ecosystem Services: A Review

“…For example, Nelson, et al [55] used a food availability module in their model to take into account the dynamic relationships between the detritus, invertebrates, algae and prey fish in-stream. Other species have also been studied, such as macroinvertebrates [57] as well as vegetal assemblages [58,59]. van Dam, et al [33] studied the multifunctional aspects of wetlands, including fish, livestock, and other agricultural production.…”