Minimum ecological water depth of a typical stream in Taihu Lake Basin, China

Minimum ecological instream water requirements are important for maintaining basic ecological functions. Characterized by its location and the effects of human activities, successful application significantly depends on the similarity in natural environment and biology. The Mengjin Stream was selected as a typical stream in the Taihu Lake Basin, which is located in the lower reaches of the Yangtze River, to calculate minimum ecological water depth (MEWD) based on the theory of eco-hydraulics. Supported by cross-section data, a method based on the relationship between river hydraulic radius and water depth is proposed. The relationship between eco-hydraulic radius R and MEWD h can be expressed by the power function h = aRb. The MEWD of Mengjin Stream is between 0.7 and 1.13 m. Assuming the average value of MEWD for these cross-sections is 0.82 m, the calculation value of most cross-sections will fluctuate between 0.81 m and 0.83 m. The variation lies in a reasonable range, which shows that the results are reliable. The calculated MEWD was validated using the water depth of Gehu Lake near Mengjin Stream. The proposed method in the present study should be validated in a different spatial scale.