Affiliation:
1. Climate, Atmosphere and Water Research Institute, Bulgarian Academy of Sciences
2. Institute of Mechanics, Bulgarian Academy of Sciences
Abstract
To maintain enough water in the river for ecosystems protection and river bed sanitation, water have to be allocated to ecosystems, as it is allocated to other users like domestic use and industry, agriculture and power generation. Water distribution is critical in dry periods. This requires proper determination of environmental flow (river ecosystem minimum permissible flow) by hydrology-based assessment methods. The purpose of this paper is to compare selected hydrological methods and to define the scientifically acceptable way to determine environmental flow within a section after the dam of some reservoirs in Bulgaria. As well as some critical reaches of the river network are determined where the necessary living environment for water communities is not provided. Here environmental flow is calculated using conventional hydrological methods: flow duration curve, the Q10% (average multiannual discharge) method and Q95% (yearly minimum monthly mean discharge with a 95% probability of occurrence) method, which are highlighted according to Bulgarian Water Law. In conclusion, the Q10% and Q95% methods allow obtaining environmental flow regimes on a monthly basis capable of adapting to the hydrological variability of the natural regime. The requirements and methods presented in the paper can be applied in the water management legislative process.
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