Use of hydrological methods for assessment of environmental flow in a river reach

Abstract

Environmental flow assessment and maintenance are relatively new practices, especially in developing countries. This paper describes the desktop assessment of environmental flows in a river with insufficient data on ecological features and values. In this study, the potential environmental flows in a typical river reach of the Shahr Chai River in Iran were investigated using a newly developed hydrological method (flow duration curve (FDC) shifting) and Global Environmental Flow Calculator software. This approach uses monthly flow data to develop an environmental FDC and to generate flow requirements corresponding to different features of the river ecosystem. Results were compared with those from four alternative hydrological methods: the desktop reserve model (DRM), Tennant, low-flow index, and flow duration curve analysis (FDCA). Comparisons of these methods indicated that to maintain the basic function of the river ecosystem, the river flows should be managed within an acceptable environmental level. The predictions from the Tennant method and the low-flow index (7-day low flow with a 10-year return period), and from the FDCA (for flows exceeding 90 % of occurrence) are not as reliable as those from the FDC shifting technique and DRM. Comparative results indicate that a minimum flow rate of 1.2 m 3 /s (equivalent to 23 % of the natural mean annual runoff, or flow with 80 % occurrence depicted from the FDC) is required for the Shahr Chai River to run toward the internationally recognized Urmia Lake in Iran.

Assessment of environmental water requirement for rivers of the Miankaleh wetland drainage basin

“…The Tennant method for seasonal rivers and especially in Fig.7 Discharge-weighted useable area for the Rutilus frisii kutum during three stages of juvenile fish, adult fish, and spawning in the Qarasu river Fig. 8 Discharge-weighted useable area for Rutilus rutilus caspicus during three stages of juvenile fish, adult fish, and spawning in the Qarasu river the arid and semi-arid climate of Iran is not suitable because it will come up with a very small value for EWR (Shaeri Karimi et al 2012). The benefits of the Tennant method are its simplicity and ease of use and its low cost.…”

“…The FDC is a cumulative probability distribution of observed flow in a stream over a long period. The FDC is represented by a plot that shows the percentage of time in which the streamflow equaled or exceeded a given value (Shaeri Karimi et al 2012). Another method of hydrological determination of the ecological water requirement is the eco-deficit method.…”

Environmental Flows Assessment in Nepal: The Case of Kaligandaki River

“…The study considers only EMC from B to F. Table 3. Description of Environmental Management Classes (EMC) used in the Global Environmental Flow Calculator [2,13].…”

A Study on the Effects of Earth Surface and Metrological Parameters on River Discharge Modeling Using SWAT Model, Case Study: Kasillian Basin, Mazandaran Province, Iran

“…The ninth row shows that when the precipitation and temperature data was not inserted, the average of mean discharge of the period decreased and the error was 70.06 percent. In the eleventh row, by omission of the solar radiation and wind speed data, the average calculated discharge showed an error of 16.72 percent [99][100][101][102][103][104][105][106][107][108][109][110][111][112][113][114][115].…”