Research on the monitoring of groundwater level movement in alluvial fan

罗库戈冲积扇位于日本北部，北纬39°25‘，东经140°34’。它占地近14平方公里。风扇头部海拔90米，外缘海拔45米，距离约4公里。Rokugo镇的中心位于边缘地带，有7000名居民。他们私自钻井，抽出未承压的地下水供家庭使用。以水稻种植为主的扇区补给地下水，作者对该冲积扇1991~1993年3年间的地下水位动态监测进行了研究。中心和外缘分别安装了深度分别为20米、50米和100米的压力计。利用压力计对水头进行了测量，得到了以下结果：(1)各深度水头差异明显；(1)各深度水头差异明显。(2)水头从地表浅点向深点递减。(3)灌水期、非灌水期、积雪期、融雪期各季节的水头差异较大。(4)地下水位变化规律为：融雪季节和5~8月灌溉活动期间地下水位较高。最高水位出现在积雪融化结束和灌溉开始时，最低水位出现在积雪达到最大值的时候，积雪深度通常在130-150厘米左右。这一研究成果将指导下一项研究项目--冲积扇地下水水位预测。

The Rokugo alluvial fan lies 39^o 25' north latitude and 140^o 34' east longitude in northern Japan. It covers an area of neary 14 square kilometers. The distance between the head, 90 meters above sea level, and outer fringe, 45 meters above sea level, of the fan is about four kilometers. The center of Rokugo town which is situated on the fringe numbers 7,000 inhabitants. They privately bore wells and pump unconfined ground water for domestic uses. Ground water is recharged in the fan's area, which is utilized mainly for rice cultivation.The author performed a study of the monitoring of ground water level movement in this alluvial fan in the three years from 1991 to 1993. Piezometers, of which depths are 20, 50 and 100 meters, were constructed at the center and the outer fringe, respectively. Hydraulic heads were measured by the piezometers.Some results are obtained : (1) Hydraulic heads clearly differ in each depth.Some results are obtained : (1) Hydraulic heads clearly differ in each depth. (2) Hydraulic head decreases from shallow point to deep point from the ground surface. (3) Difference of the hydraulic heads appears in every seasons, such as irrigated period and non-irrigated period as well snow-covered period and snow melting period. (4) Ground water level changes as follows : It is high during the season of melting snow and the period of irrigation activities from May to August. The highest level appears at the end of the melting of the snow and the beginning of irrigation, and the lowest one occurs around the time when snow cover reaches a maximum, which is usually about 130-150 centimeters in depthj.The results of the study will lead a next research project, "Forcasting Ground Water Lever in Alluvial Fan."