Baseflow studies for three rivers between Mahanadi and Godavari deltas - A research report by National Institute of Hydrology

The study suggests a procedure based on the methodology of Gustard et al (1992) for estimation of baseflow index (BFI) using the mean daily discharge data over a period of 4 to 6 years for three rivers between the Mahanadi and Godavari deltas. The rivers from the Zone 4 (A) are Rushikuliya at Purushottampur in Orissa, Nagavalli at Narayanpuram wier and Sarada at Anakapalli in Andhra Pradesh.

Baseflows (low flows) are the contribution of discharges of aquifers to the rivers and depend on drainage and geotechnical properties of the formations of the river basins. They form an important part of the available waters, especially towards the lower reaches of the watershed, as they sustain for prolonged periods of time. Surface water resource development must consider their contribution. Besides, they are important as the quality of the environment depends on their quantity.

The BFIs can be computed using a number of techniques. A computer program in FORTRAN 77 was developed under the study for the procedure to estimate BFIs as recommended in the low-flow studies report of Institute of Hydrology, UK. In the study area, BFIs range from 0.23 for Sarada (PWD site) to 0.42 for Nagavalli.

Of the three streams, it is observed that Nagavalli has a better baseflow contribution. BFIs give an indication of the geotechnical properties of the formations drained by the streams and may be used to estimate other low flow characteristics like flow duration and flow frequency. They can also be used to classify hydrology of various soil types.

The study recommends the following -

• Methodology needs to be extended to other zones along the east coast
• Need to use entire daily discharge series in such studies to arrive at dependable baseflow indices
• Monitoring agencies need to take extra care to measure the low flows during the lean season as well, so that estimated BFIs are more realistic and baseflow characteristics more reliable

Download the report here -