Approach to Land-use Analysis in Hetao Irrigation Project of Inner Mongolia, China, Based on Satellite Image Data
Takashi Kume, Kiyoshi Torii and Toru Mitsuno
Graduate School of Agriculture
Kyoto University
Oiwakecho, Kitashirakawa, Sakyoku, Kyoto
Tel. & Fax.: (81)-75-753-6459
E-mail: zak@kais.kyoto-u.ac.jp
JAPAN
Keywords : Land use analysis, Inner Mongolia irrigation project
Abstract
Hetao irrigation district is a large-scale irrigation area, which takes 294,000,000 m
3 of water annually (just less than 300 m/sec) from the Yellow River and covers 500,000 ha of agricultural field with. While this area has the history of irrigated agriculture since the time before Christ, a full-scale irrigation product was started about 100 years ago. At present, the project is said to be in a critical situation due to serious problems of water shortage and saline soil in addition to decrepitude of irrigation facilities.
In the present study, we analyzed land-use changes in the respective irrigation blocks in recent years using satellite image data to grasp the actual state of irrigation in this big project and to find a clue for solving problems in future. We present outline of the results.
Intorduction
Land-use analysis in a large-scale irrigation area is a very useful method for cropping, improvement in agricultural production, environmental assessment and irrigation-drainage planning.
Irrigation-drainage system is indispensable in arid and semi-arid areas such as Hetao irrigation district (Fig. 1) selected in this study. Agriculture without irrigation is not effected in arid and semi-arid areas where evapo-transpiration exceeds precipitation. However, inappropriate irrigation has caused soil salinization problem all over the world and this is one of the serious problems to be solved as quickly as possible. Hetao irrigation district is no exception in this aspect and the soil salinization problem is also found in this area. To solve the problem, the areas with soil salinization must be specified. However, specification of the areas with soil salinization consumes much labor, time and cost in large-scale irrigation areas such as Hetao. Thus, utilization of satellite image data, which offer monitoring in extensive areas and time-series analysis, becomes very effective.
Fig. 1 Inner Mongolia
The study area where we attempted land-use analysis based on satellite image data is Linhe City. We performed supervised classification (the most-likely classification method) and unsupervised classification to identify dunes and salinized areas in this district.
Soil salinization in arid and semi-arid areas is likely to result in desertification in future. In Hetao irrigation district in particular, Wuliangpuhe Desert is approaching from the west and continuation of irrigated agriculture in this area will consequently prevent desertification of Inner Mongolia. In this study, we attempted to grasp the situation in the salinized areas spreading around the irrigation district.
Study Area
Hetao irrigation district (Fig. 2) is located in Yellow River basin, Inner Mongolia, China, and it is 250 km in width from east to west and 50 km in length from north to south and its altitude is between 1019 and 1050 m. It has the east-to-west inclination between 1/5000 and 1/8000 and the north-to-south inclination between 1/4000 and 1/8000. It has the area of about 1,100,000 ha including 514,000 ha of agricultural area and 482,000 ha of the agricultural area corresponding to 93% are irrigated by Yellow River. Agriculture is impossible in this area without irrigation water from Yellow River. The annual precipitation in this area is between 130 and 200 mm increasing from west to east and the annual evapo-transpiration is between 2000 and 2400 mm. The highest temperature in summer is 38 °C and the lowest temperature in winter is -38 °C.
Fig. 2 Hetao rrigation district
Irrigation in this area has a long history since the time before Christ. In 1900, eight large irrigation canals were completed and the irrigation area from Yellow River became around 700,000 ha. After 1901, the Ching dynasty continued to expand irrigation area. Since the founding of People's Republic of China in 1949, Hetao irrigation district was improved rapidly. The Yellow River embankment was completed in 1950 and the irrigation area was expanded to 270,000 ha with construction of release sluice.
The irrigation area continued to expand subsequently reaching 480,000 ha in 1975. However, with expansion in the irrigated area, soil salinization in Hetao irrigation district has become a serious problem coupled with long-standing irrigation and various problems. In 1997, flow in Yellow River was cut from the river mouth to the point 700 km upstream raising a problem of water shortage. In Hetao irrigation district, salt accumulation is detected in 476,000 ha corresponding to 50% of the irrigated land of 1,100,000 ha. While salt once accumulated cannot be eliminated unless it is leached by a large amount of precipitation or irrigation water, the annual rainfall in Hetao irrigation district is extremely small as 180 to 200 mm as mentioned previously and, together with the water shortage in Yellow River, there is not sufficient water for leaching.
In this difficult situation, Hetao irrigation district has tasks of crop production with economized irrigation and rehabilitation of salinized ground. We examined distribution of dunes and salinized areas by the land-use analysis using remote sensing image data as the first step to solve these problems.
