20th Conference on Hydrology

P2.7

Streamflow characteristics and changes in Kolyma basin in Siberia

Ipshita Majhi, Univ. of Alaska, Fairbanks, AK; and D. Yang

This study documents major changes in streamflow hydrology over the Kolyma watershed due to climate variations and human impacts. Streamflow seasonal cycles over the basin are similar, with low runoff in April and peak flow in June. Analyses of mean monthly flows and trends show that reservoirs construction and operation have considerably affected streamflow regimes and long-term changes. Comparisons of mean monthly discharge records during the post- (after 1986) and pre- (before 1986) dam periods indicate that the mid-lower basin (downstream of the dam) experienced significant increases in low flows and decreases in peak flows after dam construction. For example, mean monthly flows during the post-dam period at the Ust' Srednekan station (located 1,423 km downstream of the dam) have strongly increased by about 205 m3/s (or 522 - 3157%) during December to April, and decreased by 41% (133 m3/s) in June. Long-term monthly discharge data reveal overall increases in streamflow during low flow seasons; the increases are greater for the stations located downstream of the dam. Srednekolymsk station (1,720 km from dam) shows low flow increases ranging from 130 m3/s (43%) to 268 m3/s (454%) from November to April, and high discharge decreases by 2,550 m3/s to 519 m3/s during June August in the post-dam era (1988-2000). These changes in flow patterns are caused by reservoir regulation, as reservoirs release water in winter for power generation and storage water in summer for flood control. Dam impact on flow regimes and changes are visible along the main river trunk, thus cold season discharge increases at the basin outlet is mainly the result of reservoir regulation. Annual discharge records show different changes within the Kolyma basin - with moderate increases in the upper basin and weak decreases in the mid-lower basin. Overall annual discharge at the basin outlet has decreased by 1.5% during 1978-2000. This study emphasizes the importance of human activities (particularly reservoirs) on seasonal and regional hydrology changes, and points to the need to further examine natural causes and human impacts over other high-latitude watersheds.

extended abstract  Extended Abstract (76K)

Poster Session 2, Hydrology Posters
Wednesday, 1 February 2006, 2:30 PM-4:00 PM, Exhibit Hall A2

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