HR: 0800h
AN: C41A-0180    [Abstracts]
TI: Quantifying Uncertainties in Large Scale Water Budget: Case Study in Siberia
AU: * Joe, S
EM: sjoe@umd.edu
AF: University of Maryland, College Park, Dept. of Civil & Environmental Engineering 1173 Glenn L. Martin Hall, College Park, MD 20742 United States
AU: Brubaker, K L
EM: klbrubak@umd.edu
AF: University of Maryland, College Park, Dept. of Civil & Environmental Engineering 1173 Glenn L. Martin Hall, College Park, MD 20742 United States
AB: Assessment and prediction of Arctic River flows' effects on ocean circulation and climate are hindered by lack of knowledge about the terrestial water balance in remote regions. In this study, we quantify the components of the annual water budget for a large Siberian river basin and -- most importantly -- the uncertainty in the components. The water budget for a watershed can be simplified to basic inputs and outputs: Precipitation (P), Streamflow (Q), and Evapotranspiration (E). Over the long term, assuming negligible change in storage, inputs and outputs should balance, P = Q + E. However, errors in measuring and estimating the components lead to a nonzero closure error, CE = P - Q - E. The uncertainty in the water balance can be quantified by the variance of CE, which is equal to the sum of the component variances (assumed independent). The closure error and its variance were estimated for the 57000 km$^2$ Tom River basin (a subbasin of the Ob River) for five water years, 1981- 1985. We hypothesized that (a) the CE would be negative due to underestimation of P by the sparse, low-elevation precipitation network, and (b) statistical hypothesis testing would show that the CE is not significantly different from 0, due to uncertainty in the components. The basin mean and variance of P were estimated by kriging station observations. The annual mean Q was obtained from discharge measurements at Tomsk, Russia; the uncertainty in Q was based on published estimates of rating curve error bars. The basin mean and variance of E were computed from a derived distribution based on Monte Carlo simulation of the Penman Monteith model, driven by measured meteorological data at Tomsk, and accounting for variation in elevation and vegetation. Annual CEs were negative, ranging from -160 to -325 mm, and the standard deviations ranged from 50 to 60 mm. The CE was significantly different from 0 for all five water years, supporting the belief that annual P is underestimated by the gage network. The level of uncertainty, largely due to E, makes it difficult to assess the accuracy of P. The uncertainties in the components and the CE are an indication of the confidence in statements about the water balance of the region under current or changed conditions.
DE: 9315 Arctic region
DE: 9320 Asia
DE: 1836 Hydrologic budget (1655)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting