CN107292118A - A kind of REDUCTION IN RIVERS DURING FREEZING PERIOD ecological basic flow computational methods - Google Patents

Abstract

The invention discloses a method for calculating the ecological base flow of rivers in the ice-covered period. First, based on the restoration based on the natural runoff process, the initial suggested value of the ecological base flow is proposed by using a hydrological method, and the ice-covered period is corrected according to the wintering needs of fish, and then The initial suggested value is compared with the design flow of the water function zone of the corresponding river section, the current construction and operation of water conservancy projects, and the actual flow process of the current situation, and the ecological base flow standard of key sections is comprehensively determined. This calculation method can effectively prevent the river from shrinking or even cut off, and maintain the basic stability of the river ecosystem.

Description

A Calculation Method for Ecological Base Flow of Rivers During Ice-covered Period

technical field

The invention belongs to the technical field of ecological base flow research and relates to a method for calculating the ecological base flow of rivers during the ice-covered period.

Background technique

The purpose of studying and determining the ecological base flow of a river is to prevent the river from shrinking or even stop flowing, and to maintain the basic stability of the river ecosystem. Therefore, the determination of the ecological base flow is closely related to the living characteristics of aquatic organisms, and the growth of aquatic organisms is also affected by water volume and water temperature. Restricted by other factors, the ecological base flow is not a fixed value in different periods. Generally, the ecological base flow of rivers is formulated according to the flood season and the non-flood season. The present invention combines the flow of the Songhua River Basin during the freezing period and the conditions of the freezing period and the flood season to study and formulate the ecological base flow of the Songhua River Basin from the freezing period and the non-flood season respectively.

The riverbed runoff in the Songhua River Basin has significant seasonal changes and is greatly affected by human activities. Therefore, the calculation principle for the ecological base flow of the river basin is mainly to restore the natural runoff process. The ice-covered period of the Songhua River Basin is also the overwintering period for fish organisms, so the determination of the ecological base flow during the ice-covered period still needs to consider the suitable habitat requirements for fish overwintering. However, the initial value of the ecological base flow calculated according to the natural runoff process and the overwintering demand of fish needs to be compared and analyzed with the flow demand of the water environment (the design flow of the water function area), the operation and scheduling of the water conservancy project, and the actual flow process of the current situation, so as to comprehensively determine the scientific and reasonable, The ecological base flow of the river basin as a whole with strong operability.

The calculation based on the natural runoff process first needs to use the established watershed distributed hydrological model WEPSR to accurately simulate the long series (1956-2013) natural runoff process of the Songhua River Basin, especially to realize the accurate simulation of the runoff during the ice-covered period . On this basis, the hydrological methods of ecological flow calculation (Tennant method, 7Q10 method, etc.) are used to calculate the initial value of the ecological base flow in different hydrological seasons in each river section. The Tennant method is used in the flood season.

The 7Q10 method is also called the minimum flow method. Usually, the average water volume of the driest 7 consecutive days under a 90% guarantee rate is selected as the ecological base flow of the river. In view of the characteristics of the base flow in the Songhua River Basin during the ice-covered period, this study improves on the 7Q10 method, that is, calculates the average value of the driest 7 consecutive days under the condition of a 75% guarantee rate of the natural runoff during the frozen period after restoration.

The Tennant method is a standard setting method for off-site measurements. It adopts the percentage of the annual average flow of the river and considers the recommended ecological flow value under the flow conditions of protecting fish and related environmental resources. This method is based on the flow and habitat established by historical observation data. Empirical relationships between geological qualities. According to this method, this study takes 10% of the average natural runoff for many years as the ecological base flow in the non-flood season.

For the ecological base flow of key ecologically protected river sections during the ice-covered period, it is necessary to comprehensively consider the requirements of fish overwintering for suitable hydrological elements (mainly the requirements for subglacial water depth), and establish a habitat suitability curve for fish overwintering sites. The main tributaries use the physical habitat simulation model PHABSIM to simulate the area of fish suitable wintering sites under different flow conditions during the ice-covered period, and propose the optimal value of the ecological base flow based on the protection of fish over-wintering sites during the ice-covered period, and the corresponding 50% suitable wintering site area The lower limit of overwintering flow is used as an important reference for determining the ecological base flow of relevant river sections during the ice-covered period. In other general tributaries, due to the lack of detailed river topographic data, based on the hydrological survey section in the river section, the minimum discharge requirements for relevant stations to meet the water depth requirements for fish overwintering are proposed.

After obtaining the suggested value of the ecological base flow based on the natural runoff process and fish overwintering needs, respectively, it was compared with the design flow of the water function area where the river section is located, the ecological flow formulated by the water resources protection plan of the basin, and the actual flow process of the current situation in the past 10 years. Analyze and comprehensively determine the proposed ecological base flow for each river section. The principles for determining the ecological base flow during the ice-covered period include: for river sections that are naturally frozen at the bottom in winter, no ecological base-flow requirements are set during the ice-covered period; for other river sections, the recommended value of the ecological base flow calculated based on the natural runoff process, 50% of which is appropriate The minimum value of the wintering flow corresponding to the fish wintering area, the design flow of the water function area, and the maximum value of the ecological flow formulated by the water resources protection plan of the basin are taken as the suggested value of the ecological base flow. Compare this suggested value with the daily average flow rate of 75% guarantee rate during the ice-covered period in the past 10 years. If the actual compliance rate of the suggested value in the past 10 years is too low, the reasons need to be analyzed. If the large amount of water taken leads to a low compliance rate, the recommended value should be maintained as the ecological base flow standard during the ice-covered period of the section; if the overwintering flow, design flow, or unreasonable flow in the protection plan exceeds the natural and actual flow level of the section, Based on the principle of maintaining the current flow rate during the ice-covered period, the daily average flow rate with a 75% guaranteed rate during the ice-covered period in the past 10 years and the maximum flow rate after discarding unreasonable values among the above four flows are taken as the ecological basis for the section during the ice-covered period. flow standard.

Similarly, the principles for determining the ecological base flow in the non-flood season include: using the suggested value of the ecological base flow calculated based on the natural runoff process, the design flow of the water function area, and the ecological flow formulated by the water resource protection plan of the basin as the suggested value of the ecological base flow . Compare this suggested value with the daily average flow rate of 75% guarantee rate in the non-flood season in the past 10 years. If the actual compliance rate of the suggested value is too low in the past 10 years, it is necessary to analyze the reason. If the high water consumption leads to a low compliance rate, maintain the recommended value as the ecological base flow standard of the section in the non-flood season; if the design flow rate or the unreasonable flow rate of the protection plan exceeds the natural and actual flow level of the section, maintain the current flow rate Based on the principle of no reduction, the maximum flow rate between the daily average flow rate of 75% guaranteed rate in the non-flood season in the past 10 years and the above three flows after discarding unreasonable values is taken as the ecological base flow standard of the section in the non-flood season.

Contents of the invention

The purpose of the present invention is to provide a method for calculating the ecological base flow of rivers during the ice-covered period.

In order to achieve the above-mentioned technical purpose and achieve the above-mentioned technical effect, its technical scheme is specifically as follows:

A method for calculating the ecological base flow of rivers during the ice-covered period, comprising the following steps:

Step 1. Calculation of ecological base flow based on natural runoff process

Based on the simulation results of the long series of natural daily runoff processes in the basin from 1956 to 2013 based on the WEP model of the distributed hydrology model, the ecological base flow was calculated for 57 major control river sections. First, the improved 7Q10 method was used, that is, a 75% guarantee rate The average runoff of the driest seven consecutive days is used to calculate the ecological base flow during the ice cover period. Combined with the 75% guaranteed rate of daily restoration runoff during the ice-covered period, the calculation results of the 7Q10 method are corrected;

Step 2. Ecological base flow calculation based on fish overwintering needs

The water depth of 1-1.8m is the suitable water depth for overwintering in the flowing water area, 0.6m is the minimum water depth limit, and 3m is the maximum water depth limit, and the water depth suitability curve for fish overwintering period is established; 0.01-0.05m/s is used as the suitable flow rate for fish overwintering period , 0.1m/s as the limit maximum flow rate, establish the fish overwintering flow rate suitability curve, and use the habitat simulation model to carry out the simulation calculation of the wintering suitable flow rate, considering the actual situation of the small flow rate in the ice-covered period, take the maximum wintering habitat The flow corresponding to 50% of the area is used as the wintering flow demand of fish in this river section; for tributaries without detailed topographic data, the average water depth of the measured section reaches 0.6m as the control condition, and at this time 50% of the section width can reach the fish overwintering flow requirement. Appropriate water depth, according to the flow-water level curve to calculate the flow demand of fish overwintering;

Step 3. Comparative analysis with the design flow and current situation of the water function area

Based on the calculation results of the ecological base flow of the natural runoff process, the design flow of the main water function areas corresponding to each river section is used for comparative analysis. Considering the multi-objective water allocation such as economic and social water as a whole, and at the same time comprehensively considering the scientific accessibility based on the calculation results of natural runoff and the design flow of water function areas, this study uses the actual measurements of the Songhua River Basin in the past ten years at the hydrological stations corresponding to each river section For the runoff data, the calculation results of the ecological base flow based on the natural runoff process and the satisfaction degree of the current design flow of the corresponding water function area are calculated separately, and the 75% satisfaction rate is taken as the standard of compliance.

Step 4. The verification of ecological flow during the ice-covered period

The determination of the ecological flow during the ice-covered period is mainly based on the calculation results of the natural runoff process and the overwintering flow requirements of the key protected river sections for fish, and the river sections whose calculation results are less than the design flow and the river sections whose current status is too low are checked one by one.

Further, in step 4, the final river section to be verified has the following conditions: First, the design flow rate of the water function area is greater than the calculation results based on the natural runoff process and overwintering flow rate, and the current situation satisfaction rate of the design flow rate reaches 75%. The design flow rate of the water function area is the recommended value of the ecological base flow during the ice-covered period; the second is that the current satisfaction rate of the calculation result is too low, or the gap between the design flow rate and the design flow rate is too low. In this case, refer to the 75% guarantee The calculation results of the daily runoff process measured under the ice-covered period are verified and calculated; the third is to combine topographic data, meteorological data and hydrological monitoring data.

The present invention has the following beneficial effects:

Under the existing technology, the calculation of the ecological base flow during the freezing period is often determined based on the historical natural runoff data combined with the runoff standard in the dry season. However, the freezing period of the river is also the overwintering period for fish organisms, so the determination of the ecological base flow during the freezing period still needs to be done. Consider the need for suitable habitat for fish to overwinter. The algorithm of the present invention couples the hydrological method and the fish habitat simulation method in the overwintering period, and proposes the initial suggested value of the ecological base flow of the river during the ice-covered period. Taking into account the environmental needs of aquatic organisms and the theoretical flaws of poor adaptability to river sections that are strongly disturbed by human activities, the results of ecological base flow are more accurate.

However, the initial value of the ecological base flow calculated according to the natural runoff process and fish overwintering needs needs to be compared and analyzed with the design flow of the water function area of the corresponding river section, the current construction and operation of water conservancy projects, and the actual flow process of the current situation, so as to comprehensively determine scientific and reasonable, The ecological base flow of the river basin as a whole with strong operability. To sum up, this calculation method can more effectively prevent the shrinkage of the river or even cut off the flow, and maintain the basic stability of the river ecosystem.

detailed description

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples.

A method for calculating the ecological base flow of rivers during the ice-covered period, comprising the following steps:

1. Calculation of ecological base flow based on natural runoff process

Based on the simulation results of the distributed hydrological model WEP model on the long series of natural daily runoff processes in the Songhua River Basin from 1956 to 2013, the ecological base flow calculations were carried out for 57 main control river sections. Firstly, using the improved 7Q10 method, that is, the average runoff of the driest seven consecutive days under a 75% guarantee rate, to calculate the ecological base flow during the ice cover period. Combined with the daily reduction runoff under the 75% guarantee rate during the ice cover period, the calculation results of the 7Q10 method were revised, and the results are shown in Table 1.

Table 1 Calculation results of ecological base flow during ice cover period based on natural runoff process

Analyzing the calculation results of the two methods in Table 1, the results of the ecological base flow obtained through the average runoff of the driest seven consecutive days under the 75% guarantee rate can all meet the daily reduction runoff under the 75% guarantee rate during the ice-covered period, that is, in the absence of humans In the state of activity disturbance, the reference value of ecological base flow determined by the calculation results can ensure that all river sections in the watershed can meet the runoff requirements during the ice-covered period.

2. Calculation of ecological base flow based on fish overwintering needs

During the freezing period of the Songhua River Basin, the river was frozen, low water temperature and insufficient DO supplementation after freezing were the biggest limiting factors affecting fish overwintering, and these two factors were directly affected by the water depth under the ice. According to the survey results, the water temperature at the depth of more than 1m under the ice is generally higher than 3°C, which is more suitable for fish to survive the winter; when the water depth is too deep, the growth of sediment, benthic animals and zooplankton will increase the oxygen debt layer. Large, it is not conducive to the recovery and maintenance of DO in water bodies. It is generally believed that the water depth of 1-1.8m is suitable for overwintering in the flowing water area, 0.6m is the minimum water depth, and 3m is the maximum water depth. Establish the water depth suitability curve for fish overwintering. At the same time, the flow of the water body also has a great effect on increasing DO supply, but the flow velocity should not be too large, so as to reduce the energy consumption of fish during the wintering period. s is used as the limit maximum flow rate to establish the fish overwintering flow rate suitability curve, and use the habitat simulation model to carry out the simulation calculation of the wintering suitable flow rate. The flow rate is used as the wintering flow demand of fish in this river section. For tributaries without detailed topographic information, the average water depth of the measured section is 0.6m as the control condition. At this time, about 50% of the section width can reach the suitable water depth for fish overwintering, and the flow demand of fish overwintering is calculated according to the flow-water level curve. According to the above ideas, the overwintering flow requirements of the 21 fish key protected river sections in the Songhua River Basin were calculated, and the calculation results are shown in Table 2.

Table 2 Calculation results of fish overwintering flow requirements during the ice-covered period

3. Comparative analysis with the design flow and current situation of the water function area

In order to ensure that the calculation results of the ecological base flow can reach the environmental flow, and strive to meet the sewage discharge capacity of the river section during the ice-covered period, this study is based on the calculation results of the ecological base flow of the natural runoff process, and uses the comparative analysis of the design flow of the main water function areas corresponding to each river section . Considering the multi-objective water allocation such as economic and social water as a whole, and at the same time comprehensively considering the scientific accessibility based on the calculation results of natural runoff and the design flow of water function areas, this study uses the actual measurements of the Songhua River Basin in the past ten years at the hydrological stations corresponding to each river section For the runoff data, the calculation results of the ecological base flow based on the natural runoff process and the satisfaction degree of the current design flow of the corresponding water function area are calculated separately, and the 75% satisfaction rate is taken as the standard of compliance.

Table 3 Comparison table between calculation results of ecological base flow and design flow of water function area

It can be clearly seen from Table 3 that among the 57 key river sections, the calculation results based on the natural runoff process of 28 river sections failed to reach the design flow rate, and the calculation results of some of the river sections were far lower than the design flow index value . It is necessary to further analyze the degree of satisfaction of the current situation, comprehensively consider the standards for determining the design flow rate of the water function zone and the measured runoff data during the ice-covered period, and verify the calculation results of the ecological base flow.

Through the comparison with the current situation, it can be seen that the current status of the ecological base flow based on the natural runoff process of some tributaries of the Nenjiang District, the Songganwoken River, the Tongken River and the Yinma River Basin is too low, and the design flow of some river sections It is far greater than the calculation result of ecological base flow, and the degree of satisfaction of the status quo is far lower than 75%. Therefore, it is necessary to comprehensively consider the upstream and downstream reservoirs, rivers with bottom freezing and other conditions to approve the final result.

4. Verification of ecological flow during ice cover period

The determination of the ecological flow during the ice-covered period is mainly based on the calculation results of the natural runoff process and the overwintering flow requirements of the key protected river sections for fish, and the river sections whose calculation results are less than the design flow and the river sections whose current status is too low are checked one by one. The river section that needs to be verified has the following conditions: First, the design flow of the water function area is greater than the calculation results based on the natural runoff process and overwintering flow, and the current satisfaction rate of the design flow reaches 75%. In this case, the design flow of the water function area is used as the The recommended value of the ecological base flow during the ice-covered period; the second is that the current satisfaction rate of the calculation result is too low, or the gap between the design flow rate and the design flow rate is too low, and the current satisfaction rate of the design flow rate is too low. The runoff process is verified and calculated; the third is to combine topographic data, meteorological data and hydrological monitoring data to determine that all or most of the Namor River, Yin River, Wuyuer River, Tongken River, and Woken River have been frozen. For frozen rivers, this study does not set ecological base flow indicators during the ice-covered period. The final results of the approved ecological base flow during the ice cover period are shown in Table 4.

Table 4 Summary of ecological base flow results and determination basis during the ice-covered period

The above is only a preferred specific embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any person familiar with the technical field within the technical scope disclosed in the present invention can obviously obtain the simplicity of the technical solution. Changes or equivalent replacements all fall within the protection scope of the present invention.

Claims (3)

1. A method for calculating the ecological base flow of rivers in the ice-covered period is characterized in that, comprising the following steps; Step 1. Calculation of ecological base flow based on natural runoff process Based on the simulation results of the long series of natural daily runoff processes in the basin based on the WEP model of the distributed hydrology model, the ecological base flow is calculated for the main control river sections. First, the improved 7Q10 method is used, that is, the average runoff of the driest seven consecutive days with a guarantee rate of 75% , to calculate the ecological base flow during the ice-covered period; combined with the daily reduction runoff under the 75% guarantee rate during the ice-covered period, the calculation results of the 7Q10 method were corrected; Step 2. Ecological base flow calculation based on fish overwintering needs For the ecological base flow of river sections with important ecological functions during the ice-covered period, it is necessary to comprehensively consider the needs of fish overwintering for suitable hydrological elements, establish a habitat suitability curve for fish overwintering sites, and use physical habitat simulation in the main stream and main tributaries The model PHABSIM simulates the suitable overwintering area for fish under different flow conditions during the ice-covered period, and proposes the optimal value of the ecological base flow based on the protection of the overwintering site for fish during the ice-covered period, and the lower limit of the overwintering flow corresponding to 50% of the suitable overwintering area. As an important reference for determining the ecological base flow of relevant river sections during the ice-covered period; Step 3. Comparative analysis with the design flow and current situation of the water function area Based on the calculation results of the ecological base flow of the natural runoff process, use the comparative analysis of the design flow of the main water function areas corresponding to each river section; consider the multi-objective water allocation of economic and social water use, and comprehensively consider the verification based on the calculation results of natural runoff and water function areas The scientific accessibility of the design discharge, this study uses the measured runoff data of the corresponding hydrological stations in the Songhua River Basin in the past ten years to calculate the calculation results of the ecological base flow based on the natural runoff process and the current status of the design flow of the corresponding water function area to meet the requirements Degree, with 75% satisfaction rate as the standard; Step 4. The verification of ecological flow during the ice-covered period The determination of the ecological flow during the ice-covered period is mainly based on the calculation results of the natural runoff process and the overwintering flow requirements of the key protected river sections for fish, and the river sections whose calculation results are less than the design flow and the river sections whose current status is too low are checked one by one. 2. A kind of method for calculating the ecological base flow of rivers during ice-covered periods as claimed in claim 1, characterized in that, in step 4, the river section that needs to be verified finally has the following conditions: one is that the design flow rate of the water function area is greater than that based on natural runoff The calculation results of the process and overwintering flow, and the current satisfaction rate of the design flow reaches 75%. In this case, the design flow of the water function area is used as the recommended value of the ecological base flow during the ice-covered period; the second is that the current satisfaction rate of the calculation result is too low, or If the gap with the design flow is too large, and the current satisfaction rate of the design flow is too low, in this case, refer to the verified and calculated results of the daily runoff process during the ice-covered period under the 75% guarantee rate; the third is to combine topographic data, meteorological data and hydrological monitoring data. 3. a kind of river ecological base flow calculation method during ice-covered period as claimed in claim 1, is characterized in that, in step 2, the water depth of 1-1.8m is the water depth suitable for overwintering in the flowing water area, and 0.6m is the limit minimum water depth, 3m is the limit maximum water depth, based on which the water depth suitability curve for fish overwintering is established; 0.01-0.05m/s is used as the fish overwintering suitable flow velocity, and 0.1m/s is the limit maximum flow velocity, and the fish overwintering flow velocity suitability is established accordingly Then combined with the habitat suitability curve of water depth and flow velocity, the habitat simulation model is used to carry out the simulation calculation of the suitable flow rate for overwintering. Considering the actual situation that the flow rate is small during the ice-covered period, the flow rate corresponding to 50% of the maximum wintering habitat area is taken as The wintering flow requirements of fish in this river section; for tributaries without detailed topographic data, the average water depth of the measured section is 0.6m as the control condition. At this time, 50% of the section width can reach the suitable water depth for fish overwintering. Calculate the flow demand of fish overwintering through the curve.