Suitable Environmental Flow Release Criteria for Both Human and Riverine Ecosystems: Accounting for the Uncertainty of Flows

Environmental flow (e-flow) release criteria are key parameters in water resources management and riverine ecosystem protection. The previous methods for e-flow criterion determination are based on the historical flow time series without the consideration of flow uncertainty. Due to low possibility of reoccurrence of the historical flows and the uncertainty of future flows, the flow uncertainty needs to be integrated in the process of determining e-flow release criteria. In this research, a new method is proposed to determine the optimal e-flow release criteria under flow uncertainty accounting for both the human and riverine ecosystem needs. In the new method, the scenario tree method is applied to generate the scenarios of flows, which can cover most of possible flow conditions and can effectively reflect the uncertainty of flows; the Range of Variability Approach (RVA), a most commonly used method to assess the flow regime alteration, is refined by incorporating the uncertainty of flows. The Tang River in Northern China is taken as a case study to test the effectiveness of the new method. The results show that the previous method obviously overestimates the optimal e-flow release criteria and the new method can get more suitable criteria that are suitable for both human and riverine ecosystems.