Abstract
Concern about the impacts of water regulation upon the aquatic environment has led to increasingly stringent regulatory constraints on the quantity and timing of freshwater withdrawals. For the time being these regulatory constraints tend to be articulated in terms of limits upon withdrawals, partly because of limited knowledge of the condition and resilience of the aquatic ecosystems. A more sophisticated approach to regulation would be more directly related to indicators of ecological condition. Moreover, it would consider ecosystem response to climatic events not present in the historical record. In this paper we use a combination of empirical evidence of ecosystem condition with simulation to propose and test reductions to regulatory limits on river water withdrawals and downstream minimum flow requirements. The study uses multi-level linear regression to relate the Lotic-invertebrate Index for Flow Evaluation (LIFE) to antecedent flow statistics observed in the Lee catchment, England. The selected flow statistics included extreme low (Q90) and high (Q10) flows in the summer season (April-Sept), and the median flows observed in the winter season (Oct-Mar). The derived model is used to forecast the response of the macroinvertebrate index to future flow scenarios and demand forecasts, incorporating the uncertainties in ecosystem response. Simulation is used to evaluate the sensitivity of the indices to different regulatory limits. Results indicate that macroinvertebrate health will worsen under 21st Century climate conditions, and that the existing regulation policy must be modified to maintain historically observed LIFE scores into the future. The framework demonstrates how regulations could move from precautionary limits on withdrawals to an approach based on observations, forecasting and simulation, allowing planners to refine the trade-offs between river health and reliable water supply in the face of uncertainty.
Highlights
There is mounting evidence that hydrological alteration and riverine habitat degradation influence river ecosystems (WWF, 2018), with growing demand for water threatening 65% of river habitats (Vorosmarty et al, 2010)
The results suggest that more stringent regulation is required to maintain river health along the lower Lee River in the mid to late 21st Century; an action that will likely come at the expense of maintaining water supply security
Recent research has highlighted the importance of consolidating environmental science and water planning when designing riverine management portfolios (Poff, 2018)
Summary
There is mounting evidence that hydrological alteration and riverine habitat degradation influence river ecosystems (WWF, 2018), with growing demand for water threatening 65% of river habitats (Vorosmarty et al, 2010). Increased water withdrawals throughout the 20th and early 21st Century have left rivers fragmented (Biemans et al, 2011) and with reduced flows (Richter et al, 2003). Increased risk of ecosystem damage has led to ‘opinion’ driven implementation of precautionary regulatory thresholds (Klaar et al, 2014), which typically set limits and restrict the removal of water during periods of low flow. Whilst such schemes aim to sustain riverine ecosystems (Poff & Zimmerman, 2010), they fail to reflect the dynamism of ecosystems under shifting environmental regimes (Arthington et al, 2018).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
