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Title: Impact of climate change on the Hii River basin and salinity in Lake Shinji: a case study using the SWAT model and a regression curve

Author
item SOMURA, HIROAKI - Shimane University
item Arnold, Jeffrey
item HOFFMAN, DENNIS - Texas Agrilife Research
item TAKEDA, I - Shimane University
item MORI, Y - Shimane University
item DILUZIO, MAURO - Texas Agrilife Research

Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2009
Publication Date: 4/1/2009
Citation: Somura, H., Arnold, J.G., Hoffman, D.W., Takeda, I., Mori, Y., DiLuzio, M. 2009. Impact of climate change on the Hii River basin and salinity in Lake Shinji: A case study using the SWAT model and a regression curve. Hydrological Processes. 23(13):1887-1900.

Interpretive Summary: Lake Shinji, in southeast Japan, is an economically and ecologically important brackish lake, that was recently designated as a Wetland of International Importance by the Ramsar Commission. There is concern that global climate change could cause severe environmental damage to animals and birds in the lake. In this study, a hydrologic model was used to determine the potential impact of climate change on salinity in Lake Shinji. Model results show that large increases in salinity (up to 50 percent) are possible. These salinity increases would not be lethal to adult clams, an economically important animal of the lake ecosystem, but would negatively impact reproduction of the clam. The modeling system gives policy makers a tool to estimate environmental impacts of climate and management on the lake and also develop strategies to mitigate those impacts.

Technical Abstract: The impacts of climate change on water resources were analysed for the Hii River basin and downstream Lake Shinji. The variation between saline and fresh water within these systems means that they encompass diverse ecosystems. Changes in evapotranspiration (ET), snow water equivalent, discharge into the basin, and lake salinity were determined for different climate scenarios. The impact of climate change on a brackish water clam found in the lake was then examined using simulated monthly variations of lake salinity and information from prior studies of the clam. ET increased and snow water equivalent decreased for all scenarios incorporating temperature rise, particularly during the winter season. Furthermore, ET and snow water equivalent were not as sensitive to variations in precipitation and thus temperature rise was considered to be a major factor for these variables. Nevertheless, monthly discharge volume was more influenced by variation in precipitation than variations in temperature. Discharge increased during both the summer and winter season, since precipitation contributed to river discharge instead of being stored as snow pack during the winter season. The magnitudes of salinity dilutions and concentrations predicted under the climate change scenarios would not be lethal for adult clams. However, the egg-laying season of the clam would coincide with periods of strong salinity dilution in the lake. Since juveniles are less tolerant to changes in salinity, future generations of the clam may be affected and reproduction of the clam may be reduced by increasing precipitation in the future.