1991 Fiscal Year Final Research Report Summary
Diurnal Fluctuation in Stream Flow and in Water Quality by Evapotransplration During Summer Drought Periods
Grant-in-Aid for General Scientific Research (B)
|Allocation Type||Single-year Grants |
|Research Institution||Hokkaido University |
KOBAYASHI Daiji Hokkaido University Institute of Low Temperature Science, Professor -> 北海道大学, 低温科学研究所, 教授 (30001655)
KODAMA Yuji Hokkaido University Institute of Low Temperature Science, Research Associate, 低温科学研究所, 助手 (70186708)
TACHIBANA Harukuni Hokkaido Univetsity Faculty of Engineering Research Associate, 工学部, 助手 (90002021)
ABURAKAWA Hideaki Hokkaido University of Education Associate Professor, 岩見沢分校, 助教授 (80002096)
ISHIKAWA Nobuyoshi Hokkaido University Institute of Low Temperature Science, Associate Professor, 低温科学研究所, 助教授 (70002277)
SASA Kaichiro Hokkaido University Faculty of Agriculture Professor, 演習林, 助教授 (70125318)
FUJIWARA Koichiro Hokkaido University Faculty of agriculture Professor (00001503)
|Project Period (FY)
1989 – 1991
|Keywords||Summer Drought / Water Quality / Evapotranspiration / Diurnal Fluctuation in Flow / Diurnal Fluctuation in Waterquality|
In a headwater basin covered with boreal forest in northern Japan, drought flow was observed in winter and in summer. In summer drought it was found that remarkable diurnal fluctuation of stream flow and of electric conductance is caused by daytime evapotranspiration. It was found that the daily reduction in stream flow, was accompanied by a reduction in the HCO_3^- ion concentration.
The drought hydrograph was separated into two components, assuming the drought flow to be a mixture of surface flow and of shallow flow entering the stream in its lower reaches.
(1) Caused by the deficency in rainfalls in summer in this basin, flow rate decreases exponentially from the snowmelt period to the summer drought period.
(2) Stormflow in summer low-flow period reduces more rapidly than that in snowmelt period and flow comes back onto the long-term recession trend in 2 or 3 days after storm runoff.
(3) The chemical composition of water was analyzed on HCO_3^-, Cl^-, SO_4^=, NO_3^-, Na^+ and K^+. HCO_3^- occupied about 2/3 of the total anions and Cl^- did about 1/3 in equivalent concentration. The diurnal fluctation in the stream conductance was found to be caused by the fluctuation in HCO_3^-ion concentration.
(4) The fluctuation in flow components, subsurface and shallow water was estimated to be caused by evapotranspiration near the stream channel, resulting in the diurnal fluctuation in HCO_3^- ion concentration.
Research Products (5 results)