Study On The Transport Of Soil Water And Salt Between Irrigated Land And Saline Land In Hetao Irrigation District

Under the situation that the water shortage from the yellow river water in hetao district of inner mongolia, for the influencing factor and complex process, using the barren land as the main study subject, this paper analysised the complex mechanics of water– salt translation of north barren land using field and indoor experiment. In the meantime this paper simulate the water running balance and salt convection-dispersion function using the HYDRUS-2D model. After that we disclosed the water translation mechanics of barren land in salinity area and simulated the process of salt translation. This paper also provide theoretical basis and technique supportion, so it is the rich and perfect of water-saving theory in north salinity land.The degree of salinity in hetao irrigation district is much serious and the ground water depth is much shallow because the irrigation water carry much salt but discharge less salt, so the moving of salt is warm-up between ground water and soil water. This syudy show that when irrigation water vertical infiltration and side infiltration flow, the irrigation water will vertically leach the salt into the deep soil, then the salt go to the groundwater. After that, the salt was carried into the adjacent barren land. In the meantime, the uprise salt along with uprising water make the salt gather. In salinity land without irrigation water infiltration, the salt was accomulated in the depth of 0-20cm of superfical coat. The accomulated superfical coat salt has some inhibit functions to the ground surface evaporation.This paper get some achievements as follows:1. According to observating and computating of water banlance about salinity land, include four influenceing factots: (1) irrigation water and rain capacity belonged to the irrigation land; (2)the translation of ground water; (3) soil evaporation function; (4)water space variation of salinity soil. In the process of crop tilth irrigation, the soil water is balance, the rain and irrigation water were consumed by soil evaporation. The barren land without irrigation water will acomulate the salt from the irrigation land. So the barren land became temporary discharge salt area. The salt accomulated in the depth of 0-20 cm of superfical coat, has some inhibit functions to the ground surface evaporation.2. Through observating and computating the salt space variation, we can define the salt accumulation and leaching balance. The degree of barren land salinity: increase during the crop growing time, decrease during irrigation leaching in fall, keep balance with the adjacent irrrigation land during the land become thaw in the next year. Because the space variation of soil and salt is higher, so rainfull,irrigation water,evaporation and groundwater have many influences to them. (1)The volume of irrigation water has direct influenceto the salt volume change of barren land: the much irrigation water the more level leakage,the higher level of ground water, the much accumulatedn salt . And vice versa is also. (2)In the case of rainfull but without accumulated water, the farmland salt decrease, the barren land salt was leached. If the surface coat has accumulated water, the farmland salt does not have significant difference. But if the farmland was immersed by the accumulated water for a long time, it will lead to salt in the ground water uprise surface land. so the barren land salt decrease and the ground water salt increase. (3)Under the situation of evaporation force does not change and ground water salt keep balance, the more shallow of ground water depth, the much salt was accumulated in the surface soil.3. The degree of soil salinity is warm-up and it is a contact with the ionic species. Salt -barren land and farmland in the depth of 0-100cm contain a great deal of Caionic. Salt-barren soil in the depth of 0-100cm have much water solubility salt ionic. After rainning, the soil contain less salt especially the surface soil water solubility salt ionic which was leached into the deep soil. From the annual change, we can see that water solubility salt ionic does not have much change, but non-solvent salt farmland and barren land changed much.4. The influence of rainfull to the soil matrix changed along with the soil depth. The change of matrix along with time follow periodic add-subtract regular pattern, and the periodic time is 24h. The change of soil matrix is small. The soil temperature is the main factor to the matrix change when water-content coefficient change less.5. Field and indoor experiment separately rate the soil water movement characteristic parameters. We also standardizated the field actual measurement soil matrix. Then we established mathematic model for the soil matrix and saturation degree.6. The HYDRUS-2D model simulated the soil water-content coefficient, the gap between simulated value and measured value is small, so the fitting result is good. The fitting result of soil content is not very good especially in the surface soil depth of 0-20cm. The simulating research on soil water-salt translation changing is reasonable and credibility during early days irrigation. This modle can also objectively simulate and reappear the water-salt translation regular pattern for the early day irrigation.The fall irrigation leach much salt accumulated during the irrigation time and lysis the degree of salinity for the irrigation district. For farmland, fall irrigation can leach salt. Then it provide space for the salt accumulated in the next year.The HYDRUS-2D model, which simulate the process about the space variation of water-salt during irrigation time, after rating analysis, can reliably disclose water-salt transfer regular pattern of the barren land distributing on the interspace farmland. This paper provide proof for the research about soil water-salt transfer of farmland and barren land. This paper also can be used for the model of HYDRUS-2D simulation and research basis to the salinity land.