Abstract:
Base flows or low flows form an important part of available waters, especially towards the lower reaches of watershed, as they are the flows sustaining over a prolonged period of time. Any water resources development of available surface water must consider the contribution of these low flows. As the low flows are the contributions from the discharges of the aquifers to the rivers, they depend on the drainage and the geotechnical properties of the formations of river basin. Low flows are important as the quality of the environment depends on the quantity of low flows occurring particularly in areas of urban living and having check on pollution.
Base flow studies can be undertaken by a number of techniques. The purpose for which the study is being undertaken mainly determines the particular procedure to be adopted. In this study a procedure as suggested in the low flow studies report of by Gustard et.al, 1992 to estimate the Base flow Index using the mean daily discharge data is employed for three rivers of Zone 4(A) and baseflow indices are developed for three east flowing rivers namely the Rishikulya at Purushottampur in Orissa, the Nagavali at Narayanapuram Wier and the Sarada at Anakapalli in Andhra Pradesh using the daily flows over a period of 4 to 6 years. The indices indicate the contribution of the baseflow to the total available flows on these streams.
A computer program in FORTRAN 77 is written for the procedure to estimate BFI's as recommended in the Low flows studies report of Institute of Hydrology, UK. The BFI's thus arrived at are varying from 0.23 at the Sarada (PWD site) to 0.42 for the Nagavali. Among the three streams studied it is observed that Nagavali has good baseflow contribution.
