To reasonably determine the ecological flow for rivers in Beijing

a calculation method system was constructed based on a systematic review of concepts and calculation methods of ecological flow at home and abroad and an overall consideration of the characteristics of Beijing's river channels. The system divided rivers and lakes in Beijing into two categories: those less disturbed by human activities and those more disturbed by human activities and proposed the suitable ecological flow calculation method and the recommended values of calculation parameters for each category. For less disturbed rivers and lakes

mostly natural ones

the ecological flow is the minimum amount that needs to be retained in the river channel

which is calculated by adopting the Tennant method

runoff depth isoline method and area comparison method. For more disturbed rivers and lakes that need artificial water replenishment

the ecological flow is the sum of water volume that maintains the water surface area of rivers and lakes and water volume that maintains ecosystem functions

with the former calculated using the quota method

and the latter calculated using the multilevel balance method for the realization of functions and objectives of rivers and lakes such as preserving river ecosystems

ensuring water quality

maintaining landscape and water recreation

and assuring river navigation. Besides

the Juma River

the Beiyun River

and the Liangshui River were used as examples to illustrate the calculation of the ecological flow of various rivers.