Identifying representative watershed for the Urmia Lake Basin, Iran

Area of Science:

• Hydrology and Water Resource Management
• Environmental Monitoring
• Geographic Information Systems (GIS)

Background:

• Designating representative watersheds (RWs) is crucial for cost-effective monitoring of watershed performance against various drivers.
• This is particularly important in developing countries with limited investment and increasing human impact.
• The selection of RWs has been historically underemphasized globally, especially in developing nations.

Purpose of the Study:

• To develop a quantitative method, the Representative Watershed Index (RWI), for selecting representative watersheds.
• To apply this method to the Urmia Lake Basin (ULB) in Iran as a case study.
• To identify a suitable RW for future monitoring and adaptive watershed management in the ULB.

Main Methods:

• Formulated a quantitative Representative Watershed Index (RWI) ranging from 0 to 100.
• Utilized national-wide raster data including elevation, slope, rainfall erosivity, and land use.
• Employed matrix programming in MATLAB and GIS software for data overlay and RWI computation across 61 sub-watersheds.

Main Results:

• Computed RWIs for 61 sub-watersheds in the Urmia Lake Basin, with values ranging from 5.54 to 53.46.
• Identified sub-watershed No. 57 with an RWI of 40.65 as the final representative watershed.
• The selected RW (No. 57) was chosen based on hydrological independence, suitable location, and the presence of operational monitoring stations.

Conclusions:

• The developed RWI provides a robust, quantitative approach for selecting representative watersheds.
• The identified RW for the Urmia Lake Basin serves as a basis for future monitoring and adaptive management.
• This method offers a cost-effective solution for watershed assessment, especially in regions with resource constraints.