Design code for small hyower station English
1 General Provisions
1.0.1 This Code is formulated to satisfy the needs for construction and development of small hydropower stations in China, with the purpose of following technical advancement and sharing experiences in construction of hydropower stations, so as to standardize technical specifications and improve quality of design.
1.0.2 This Code is applicable to designing of small hydropower stations (hereinafter referred to as“hydropower stations”) with an installed capacity of 0.5-50MW that are newly built, upgraded and rehabilitated.
1.0.3 Design of hydropower stations shall be in line with integrated plan of river basins or hydropower plan of river and river reaches.
1.0.4 Design of hydropower stations shall be made in compliance with the country’s current technical and economic policies；while overall consideration shall be given to local conditions of water resources, hydropower, navigation, soil and water conservation and environmental protection, as well as electricity market.The design shall take the local conditions into full consideration for rational utilization of water resources.
1.0.5 Investigation, research and reconnaissance shall be carried out for the design of hydropower stations, in order to gather basic information and data related to hydrology, meteorology, geography, geology, construction materials, power grid, land requisition, resident resettlement, environmental protection, soil and water conservation, river exploitation and water use of various industries.
1.0.6 Provisions stipulated not only in this Code but also in the prevailing national standards shall be complied with in the design of hydropower stations.
2 Hydrology
2.1 General Requirements
2.1.1 In hydrological analysis and computation, the following data shall be collected: hydrological and meteorological data and natural geographical features of both the basin in question and its neighboring basins, information about the impact of human activities on the basin in question such as development of water and hydropower projects and soil and water conservation, data of regional historical floods, and comprehensive analysis and research of regional hydrological and meteorological information, etc.
2.1.2 The basic data on which hydrological computation is made shall be analyzed for its reliability, consistency and representativeness.Parameters, analysis and computation results adopted shall be examined for their rationality.
2.2 Runoff
2.2.1 Computation of runoff shall provide all or part of the following information at dam site:
1 Annual, monthly, 10-day and daily runoff series, and mean annual runoff.
2 Annual and periodic runoff frequency.
3 Intra-annual distribution of runoff in typical design year, and duration curve of mean daily runoff, etc.
2.2.2 Design runoff shall be calculated by the following methods based on the data available:
1 If the consecutive data of runoff series (including extrapolation)is available for more than 30 years for the dam site, the design annual and periodic runoff shall be calculated directly by the method of frequency computation.
2 If runoff data for dam site is available for less than 30 years, but there is more than 30 years of runoff data (including extrapolation)for the upper, lower or neighboring basins, the design runoff of a reference station in the above-mentioned basins may be applied to the dam site after being revised based on the differences at catchment area, precipitation and underlying surface condition.
3 If there is no runoff data in the design river basin while the precipitation data is available, the runoff may be derived by analyzing the relationship between the precipitation and runoff at a hydrometrical gauging station in a similar river basin nearby.
4 If none of the above-mentioned data is available, the regional comprehensive method may be used for the computation of design runoff.
2.2.3 If the runoff is affected by human activities in the basin upstream of the cross-section of the design runoff, the extent of impact shall be investigated and analyzed, and restoration computation shall be done for the runoff data.If restored flow data is insufficient, the computation of design runoff may be done by analyzing the direct statistics of actually measured runoff series that have been impacted by human activities, or by the runoff computation method in case of data shortage .
If the actually measured runoff data is insufficient, the method such as correlation analysis may be used for runoff series extrapolation.
If correlation analysis is used for runoff series extrapolation, the correlation coefficient should be larger than 0.8. The years for extrapolation series should not exceed the years of series used in the correlation analysis.
2.2.4 The time period for runoff computation may be selected as annually or periodically (for non-flood season or dry season)according to the design requirements.Innconsecutive runoff series, the mth empirical frequency in descending order, i.e.Pm, shall be calculated by the formula below:
The Pearson Type Ⅲ frequency curve may be adopted, and the statistical parameters may be estimated initially by using the moment method and then adjusted and defined by the curve fitting method.
2.2.5 If the runoff computation is made by using regional comprehensive method, the regional precipitation runoff approved by the competent authorities, isoline map of statistical parameter or empirical formula for runoff computation shall be used.
2.2.6 With regard to the selected annual runoff series, their representativeness shall be analyzed by comparing the statistical parameters of long and short series on the basis of data gathered by regional hydrometric gauging stations and precipitation gauging stations.
2.2.7 With regard to the intra-annual distribution of runoff in the typical design year, the actual year with its empirical frequency of annual and periodic runoff similar with the design frequency may be selected as the typical year, and then amended and determined by using the design runoff.
If the actual measurement data is limited, the annual distribution of runoff in the typical design year may be derived by available regional integrated charts of runoff.
2.2.8 If a river where the hydropower station is located has special hydrological and geological conditions, their impact on the design runoff shall be analyzed and studied.
2.2.9 In calculation of mean daily discharge duration curve, the following methods may be used depending on data available:
1 Statistics by sorting the mean daily discharges in three typical years with high flow, normal flow and low flow.
2 Adjusted mean daily discharge duration curve at a reference station calculated based on catchment area and precipitation of the site of hydropower station.
2.2.10 The result of runoff analysis and computation shall be compared with the computation results of upstream, downstream, main stream and tributaries, and adjacent basins so as to analyze and check its rationality.
2.3 Flood
2.3.1 All or parts of the following design flood results at dam（plant）sites shall be provided as required for the design of hydropower stations:
1 Annual maximum peak discharges of design floods with different frequencies and their maximum volumes in a period of time.
2 Seasonal maximum flood peak discharge and flood volume in a period of time by each design flood frequency.
3 Annual and seasonal design flood hydrographs by each design flood frequency.
