On the Mechanism of Hydrological Cycle in Reclaimed Upland Fields

Research Project

Project/Area Number	60460211
Research Category	Grant-in-Aid for General Scientific Research (B)
Allocation Type	Single-year Grants
Research Field	農業土木
Research Institution	Kyoto University
Principal Investigator	MARUYAMA Toshisuke Faculty of Agriculture, Kyoto University, 農学部, 教授 (90026451)
Co-Investigator(Kenkyū-buntansha)	WATANABE Tsugihiro Faculty of Agriculture, Kyoto University, 農学部, 助手 (50175105) KOBAYASHI Shintaro Faculty of Agriculture, Kyoto University, 農学部, 助教授 (20026602)
Project Period (FY)	1985 – 1987
Project Status	Completed (Fiscal Year 1987)
Budget Amount *help	¥7,300,000 (Direct Cost: ¥7,300,000) Fiscal Year 1987: ¥1,000,000 (Direct Cost: ¥1,000,000) Fiscal Year 1986: ¥1,300,000 (Direct Cost: ¥1,300,000) Fiscal Year 1985: ¥5,000,000 (Direct Cost: ¥5,000,000)
Keywords	Water Cycle / Agricultural Land Reclamation / Flood Runnoff / 低水流出 / 水循環機構 / 流出モデル
Research Abstract	Not only geographical features but also structures of water cycle of river catchments change due to the land reclamation works. And these changes lead the change in runoff properties. To examine this, three small runoff test plots (two of them are reclaimed upland fields and the rest is forestry area) were set in the Tango national reclamation project area in northern part of Kyoto prefecture, and soil and runoff experiments were conducted in these plots. The results of soil tests in both the reclaimed and the non-reclaimed plots are as follows; 1. Water holding capacity has been lowered due to the removal of A0 and/or A1 horizons and the increase of the solid-phase percentage of soil after the reclamation. 2. Soil permiability has been also lowered due to the various reclamation works with the large construction machinery. 3. Construction of water channels and farm roads have also led to the decrease of permiability and water holding capacity of reclaimed plots. The results of investigations for the runoff properties are as follows; 1. Peak discharge increased much due to the reclamation. Thiswas a reflection of the decrease of concentration time and the increase of coefficient of peak discharge which were led by the change in soil physical properties described above. 2. Though change in low water properties has not been clarified yet because of the shortage of hydrological records during the investigating periods, a slight change in the recession constant of discharge have been recognized. 3. Settling basins constructed in the downstream of reclaimed plots have been much efficient both for fllog control and for low-water supplement in drought seacon.