Estimation of Ecological Water Requirements Based on Habitat Response to Water Level in Huanghe River Delta, China

In recent years, wetland ecological water requirements (EWRs) have been estimated by using hydrological and functional approaches, but those approaches have not yet been integrated for a whole ecosystem. This paper presents a new method for calculating wetland EWRs, which is based on the response of habitats to water level, and determines water level threshold through the functional integrity of habitats. Results show that in the Huanghe (Yellow) River Delta water levels between 5.0 m and 5.5 m are required to maintain the functional integrity of the wetland at a value higher than 0.7. One of the dominant plants in the delta, Phragmites australis, tolerates water level fluctuation of about +/- 0.25 m without the change in wetland functional integrity. The minimum, optimum and maximum EWRs for the Huanghe River Delta are 9.42 x 10(6) m(3), 15.56 x 10(6) m(3) and 24.12 x 10(6) m(3) with water levels of 5.0 m, 5.2 m and 5.5 m, corresponding to functional integrity indices of 0.70, 0.84 and 0.72, respectively. A wetland restoration program has been performed, which aims to meet these EWRs in attempt to recover from losses of up to 98% in the delta's former wetland area.