GISdevelopment.net ---> AARS ---> ACRS 1992 ---> Poster Session Q

Remote Sensing Monitoring of Land Utilization and Salinization for Decade Dynamics in Hetao Irrigation Area of Inner Mongolia Autonomous Region

Wang Wen-sheg, Xiao Dong, Guo Ri – Qin, Li Ning, Wang Zhi, Guo Jin – sheng
Institute of Water Conservancy of Inner Mongolia
Autonomous Region Hubhol china post No. 010020


Abstract
Applying Remote Sensing information from USA Landsat of interval decade, dynamic monitoring has been carried on for land utilization and salinization in Hetao irrigation. Area of Inner Mongolia Autonomous Region. We have had a good command of changeable circumstance from 1976 to 1987 and its developing tendency inside this irrigation area provided basis for making strategic decision to administrative department exploiting in harness and restrict Hetao Irrigation Area, Meanwhile, a new technique of surveying and mapping i.e “appoying integrated base map can be derived from different combination of coded spots,” has been inquired into and sum up in the course of the studying, this kind of new and original mapping has developed new technology of Remote Sensing interpretation and cartography.

. Purpose of studying
Hetao Irrigation Area of Inner Mongolia Autonomous Region is an age-old diversion irrigation area from Huanghe River, possessed favourable conditions for developing irrigation farming on account of smooth terrain, facilitated irrigation and full of sunshine. However, salinization of soil has been restricting the development of agriculture and livestock farming and further exploite and use land in this area.

Since 1970’s this area ahs been listed one of priority commodity grain bases of our country, Irrigation and drainage system has been constructed to going on at accelerated pace for harnessing and improving he salinization of the soil. In order to monitor quickly the dynamics of salinization of soil and to keep abreast of the developing and changeable tendency in the process of construction and harness in the irrigation area, we have studies and approached to development, change and dynamic tendency of land utilization and salinization of soil for this decade in this area by means of Remote Sensing survey technology to wield the Landsat information from both of different phases of time from 1976 to 1987. On point of view of macroscopic, some strategic decisions and basis have been provided for administrative departments and prodacer’s unit to exploit and harness Hetao Irrigation Area and to construct the commodity grain bases. These achievements in scientific research have come up to advanced world standards by expert’s identification.

II. Technical Process of Interpretation and Cartography
Having applied the technical process of optical treating satellite image and visral interpretation cartography, MSS photographic in 1976 and TM photograph in 1987 has been used separately one after another to survey and compile three kinds of map for land utilization, types of soil and salinealkali harmfulness, According to these techniques, we have studied and approached the change of soil salinization and developing tendency for this decade on analyze and contrast in Hetao Irrigation Area.

For the sake of centralizing the spot’s bound of above – mentioned three kinds of map concertedly each other on a definite base map, embodying possession of geographic interrelation in condition of each other to existence and transform of various ground as well as make simplification of interpretation and cartography, we have summarized a new method of “applying integrated base map coding primary spot only once deriving thematic map from different combination of coded spot”. This new technique has both simple and convenient in interpretation and cartography, Unified various thematic maps on the base map. It will be introduced briefly as follows :

1. Determining classification system of basic map
in the lighe of physiographic general situation and covering condition of ground surface in this local, two or three degree’s classification system should be determined and coded in order for different types of geomorphy, soil and surface’s texture and covery, The kinds of every map had better to be less than 9 types.

2. Interpreting and compiling base map of primary spot coding.
At first, a primary interpretation needed to be carried out so as to learn about the image features of every type spot and to establish interpretation key confirmed by field check. On the basis of analyses and interpretation to comprehensive factor according to different categories attribute element belong to various essential types, we can identify the classification property to each kind of primary spot for geomorphy, soil, texture and coverage, then combined and coded with the property’s number.

3. Compiling thematic map
In the first place, classification system of one two or three degrees of various thematic maps should be thoroughly determined in order to additional operation of combination for primary spot coding. Then drawing clearly should be carried out along with along with new spot’s bound or distinguished the new combinized. Spot’s bound by different colours on the original base map.

III. Evolution in Times and Space and Tendency Analysis of Cuotivated land and Saline –alkali Waste Grassladn in Hetao Irrigation Area.

1. Evolution and tendency
Viewing the situation as a whole, this irrigation area has been developing to the better tendency analysised from both of different period’s survey data. In this decade the area of salinization waste grassland has been reduced by 179. 5 thousand mu, on an average, there was a progressive decrease of 16.3 thousand mu a year. And the are a of cultivated land has been developed 93.2 thousand mu. There was an increase by degrees of 8.5 thousand mu every year.

However, compared with different regions of this irrigation are the cultivated land and salinealkali waste grassland were absolutely not to increase or decrease consistency since condition in these regions differ in topographic position, condition of irrigation and drainage and human being’s production action. Developing tendency of these regions was either increase or decrease some regions has been tending toe be better and other ones to be worse. What regions changed obviously are located in the south-western part ad north-eastern part in the irrigation area, As it is located in upper reaches of the area, which drainage system toe b constructed a set comparatively so well as which surface runoff and ground water runoff to be unobstructed, so the former has been trending to be better, with increasing the area of cultivated land of 173 thousand mu and decreasing the area of salind – alkali waste grassland of 171 thousand mu precociously, the latter is opposite to the former. As it is located in lower topographic position and in lower reaches of the area, being often higher above ground surface the groundwater level of the Trunk Drain to make if seep into the two side river bank in versely, also permeating into this region since it is higher water level of Wulinagsuhai lake near by the end of the area, possessing some drainage system but not to form a complete set even not to drain gravitatively, there is still higher ground water level in this region, and development of salini-alkali soil is for out of control and tent to be worse continuously, there is an increase in the area of saline-alkali land of 107. 4 thousand mu and a decrease in the area of cultivated land of 113.7 thousand mu in the decade, after changing the system of agricultural administration since 1980, as a result of peasants’ intensive cultivation, above – mentioned circumstance has been begun n tending to be well but the changeable range was smaller year out until 1987, with peasants having idarnt about the country’s policy very well and bring into some plays of these drainage system.

2. Environmental regularity of salinization
Up till now, in the condition of that the drainage system still not to be put a set and the ground water level not to descend to an appropriate standard, the evolution and development salinization o soil has been restricted chiefly by factors of topographic condition, managerial degree of land exploiting and utilization and the proportion of irrigation to drainage in the area . only did anlaysis the factor of salt taken along the irrigation water to be diverted from Huanghe River, this area are still in state of accumulate salt as irrigation more than derange. On the conduction effect of soil water osmosis pressure, the salt expands and moves to cultivated land and salinity wasteland in all directions which not to be irrigated or to e lower ground water level, formed plain transform within different topographies and cultivated land to wasteland “salt some along water ad go to with water”, “more waste land, more severre salinization” These two peasants proverbs have summarized the evolutional regularity of salt moving and tendency of developing of salinziation in Hetao Irrigation Area.

3. Restrictive factors of salini – alkali development
forming and developing of salini-alkali soil has either internal cause or external cause in Hetao Irrigation Area, since this are locates in interior fault subsidence lake - basin of arid region, ground water runoff is not to pass unimpeded, inevitably leading to innense quality of soil salt in deeper layers such hydrogeological circumstances developing irrigation farm may be internal cause to bring about salinziation. And arid climate with characteristic of annual quantity of fewer precipitation and more evapotranspiration would be external pause of lead to salinization. No rational management of flood irrigational management of flood irrigation artificial, raising the ground water level, has accelerated the course of development of salinziation in this natural environmental. Knowing the cause of salinziation well, having a good command of evolutionary regularity of one’s development and change, accelerating to construction of the drainage system, improving the adverse circumstance of hydrogeography, exploiting and using the land reasonably and irrigation in scientific method development of salinization in Hetao Irrigation Area would be able to be controlled and soil to the ameliorated gradually too. Land exploitation and utilization will have great potentially in Hetao Irrigation Area and will have bright prospects for development of National economy.