中国オルドス高原杭錦旗の連環井とその技術的応用について On "Lianhuanjing" in Hangjin Qi, Ordos Plateau, China and Its Technical Application
A special groundwater collector system, termed "Lianhuanjing", exists in Hangjin Qi, Inner Mongolian Autonomous Region, on the Ordos Plateau, China. The author investigated "Lianhuanjing" on its development history, size, function, water quality, etc. More than 60 "Lianhuanjing" exist on the top of the hill at elevations of 1, 450 to 1, 600 meters above sea level, where little groundwater recharge occurs and only fissure water is expected.<BR>Hangjin Qi has only 150-300 mm of annual precipitation, about 3, 000 mm of potential evapotranspiration and is an arid climate typical of deserts and steppes. Major droughts have very often occurred there as shown in Table 1. As it was very difficult to obtain water, farmers living there developed a unique groundwater collector system known as "Lianhuanjing". "Lianhuanjing" may be described as a "chained collector well system" from a functional point of view.<BR>The length of the first "Lianhuanjing", constructed in 1959 and completed in 1962 at Ganhaiz, Shengli Village, Hangjin Qi shown Fig. 2, was 1, 200 meters and contained 300 vertical holes. Each 4 m-interval-hole was the hole from which earth and sand was thrown away. An ideal arrangement of "Lianhuanjing" is linear and goes direct to groundwater flow for collecting water efficiently. Water volume brought from "Lianhuanjing" was limited, but extracted water contributed to the local development of agriculture. After the favorable performance of the first "Lianhuanjing", a lot of "Lianhuanjing" were constructed. But during and immediately after the "Cultural Revolution", new "Lianhuanjing" were constructed. Several reasons, such as the collapse of the people's commune system in China, the privatization of agricultural land, and the introduction of new technology for drilling wells encouraged farmers to construct many new, small-scale "Lianhuanjing" systems after 1989. The arrangement of the "Lianhuanjing" constructed after 1989 was a geometrical distribution as shown in Fig. 6. This was the reason why farmers thought such an arrangement of the wells could collect groundwater more efficiently than the linear arrangement in case of getting fissure water in limited agriculture land.<BR>Quality of groundwater withdrawn from "Lianhuanjing" was Ca-HCO<SUB>3</SUB> type, but contained quite high nitrate concentrations, over the drinking standard. Sodium Adsorption Ratio (SAR) was less than 1, and the value was judged as good only for irrigation.<BR>"Lianhuanjing" is a special and unique groundwater collector system combining vertical holes with lateral ones, found only in Hangjin Qi, to obtain fissure water. There are two other similar irrigation facilities, such as the Kanat system and the so-called "Manchulian well", but "Lianhuanjing" is quite different from others as shown in Table 3. However, the technology of "Lianhuanjing" is quite valuable even for Japan as it is applicable to the places where the sandstone bedrock is rather shallow and groundwater resources is limited.
地學雜誌 105(2), 163-177, 1996-04-25
Tokyo Geographical Society