Ecological flow calculation method | Formula for calculating ecological flow assurance rate

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How to calculate the ecological water demand in rivers?

1. Tennant method: Tennant method is a commonly used method for estimating ecological water use in rivers, also known as Montana method. It is based on the principles of hydrology and aims to protect fish, wildlife, and environmental resources, and recommends river base flow. This method is suitable for evaluating water resource development and utilization, recommending river flow, or as a validation for other methods. The Tennant method categorizes ecological water demand into 8 levels, ranging from "extremely poor" to "maximum", and recommends the percentage of average annual flow for each level. By calculating the average annual flow rate and the corresponding level percentage, the ecological water demand for each period of the year can be easily calculated. The total water demand can be obtained by summing up the whole year. 2. Q90 method: The Q90 method is derived from the 7Q10 method in the United States and is used to determine the ecological water demand in rivers. The minimum flow design value is the average flow rate of the driest continuous 7 days with a 90% guarantee rate. A study by the US Environmental Protection Agency shows that the results of the 7Q10 method are similar to those of the 4B3 method, therefore it is recommended for use in water quality standard design flow. Since the 1970s, China has introduced the 7Q10 method and adjusted it according to its national conditions, usually using the average flow rate of the driest month or the average flow rate of the driest month with a 90% guarantee rate. The Q90 method takes the minimum monthly average flow rate with a 90% guarantee rate as the ecological environment water demand value, wh

ich is calculated through frequency to obtain the annual ecological environment water demand. 3. Wet week method: The wet week method is a hydraulic based method for calculating water ecological water demand. This method believes that the wet cycle increases with the increase of flow rate, but after exceeding the critical value, the wet cycle is not sensitive to changes in flow rate. Protecting the critical wet zone can meet the basic needs of aquatic habitat protection. The wet cycle method uses the critical wet cycle of rivers as an indicator of aquatic habitat quality, taking into account the influence of river shape, and is suitable for wide and shallow river channels. The key to calculation is to determine the flow wet cycle relationship, which is determined through river section data and water level flow relationship. Find the critical point flow value in the flow wet cycle relationship diagram as the flow value to maintain the ecological water demand of the river channel, and calculate the annual ecological environmental water demand.

2. Calculation formula for ecological flow assurance rate

The calculation formula for ecological flow assurance rate is: ecological flow/total flow x 100%.

. The ecological flow guarantee rate reflects the proportion of water flow set up in a chain to maintain the ecological environment of the watershed to the total amount of water resources in the watershed. This ratio is determined by calculating the annual average flow or minimum flow to ensure the basic needs of aquatic ecosystems. The total flow refers to the natural runoff or the total amount of water replenished within the watershed. When the ecological flow guarantee rate increases, it means that the ecologi

Ecological flow calculation method | Formula for calculating ecological flow assurance rate

How to calculate the ecological water demand in rivers?

2. Calculation formula for ecological flow assurance rate

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