Climate change impacts on water resources in the Nechako River Basin, BC.

Abstract:

The Nechako River Basin (NRB) is the second largest watershed of the Fraser River Basin covering 52000 km² areas. The basin is highly regulated, used for power production and vital for the communities, environment, and economy of the northern British Columbia. Climate change and its impacts are already being experienced in the NRB such as increased temperature and decreased number of snowfall days. This study addresses how a warming climate leads to changes in surface water availability across the NRB. We perform a climatology and trend analysis of water budget terms for the NRB including precipitation, river runoff, and evapotranspiration using observed data from 1950 to 2010. Furthermore, we analyze the future changes in these parameters using statistically downscaled data of CMIP5 climate models for RCP8.5 scenario focusing 2050s and 2080s time slices. Mann-Kendall trend test is used for the trend analysis. We find that during the last six decades, annual mean temperature of the NRB has risen by 1.17°C, and the contribution of snow to the runoff has significantly declined. The runoff to precipitation ratio shows significantly decreasing trend of 0.02 per decade. Further, with significant increase in temperature by 2080s, the NRB may shift from snowmelt to a rainfall-dominated system. This alternation has potential to adversely affect a range of water-dependent resource sectors. This study is expected to advance the understanding on the hydrological changes in the NRB and help to improve management of water resources.