Trends analysis on eco-hydraulics indexes of the mainstream of the Yellow River

Ecological hydraulics indexes such as water level, water depth and cross-section shapes etc., contain important ecological information, so studying the evolution process of these indexes is very significant to study the development trends of river ecological system under the influence of human activities in the future and formulate the rivers protection strategy. Through analyzing the eco-hydraulics indexes on Tangnaihai, Lanzhou, Toudaoguai and Huayuankou cross-sections of the mainstream Yellow River, it was found that water level inter-annual variability at Tangnaihai and Toudaoguai sections presented a decreasing trend, no change at lanzhou, and increasing slightly on Huayuankou section. Water level swelling and recession on each section was basically stable in a year, within no obvious change. As time goes by, the variation of water depth without a year leveled off, extremely peak and low water level decreasing, and even draught-up of river was exist during May to July on Toudaoguai and Huayuankou section. On the aspect of river cross-section shapes, the large alteration mainly occurred at Huayuankou and Toudaoguai sections.