A Study of Factors Influencing Land Degradation,

Decrease in land potential, land degradation, happens due to various factors. One of the important factors causing degradation of lands and desertification is soil and water salinization that occurs in arid and semi arid regions. Factors influencing soil and water salinization are natural as well as anthropogenic. The main objective in this research was to get knowledge of saline soils as well as to study the factors affecting land degradation and soil salinization in Varamin Plain. Towards this aim, surface water, groundwater, land use, geology, and soil factors were studied. First, the limit of watershed was determined, and then with the help of geology and topography maps as well as satellite images together with field-work, saline soils and factors affecting land degradation were made known. Land use condition (with the help of remotely sensed data and field-work) was obtained. With the use of land use map, satellite imaging and remotely sensed data, geology and topography maps, the homogenous units were obtained on the satellite imaging. Soil sampling in these units was done and EC and SAR parameters obtained. Then with help of GIS, iso_EC and iso_SAR were obtained. With the use of in-use and pizometer wells data and hydrometery stations, ground and surface water were studied and influences of each on land degradation determined. Also, influences of geology formations on surface water and groundwater were studied. Results indicated that wide regions of south, southwest, southeast, northwest and west of Varamin plain were degraded. From margin to central plain the degree of land degradation and salinization was decreased. From center to northeastern part of the plain there isn’t any serious salinization observed. Also, the studies revealed that climatic conditions, rise of water table, use of saline water for irrigation, unauthorized deep well excavations, improper exploitation of groundwater sources, intrusion of urban and industrial sewage in to Jajrood river, entrance of irrigation drainage water in to river, management, lock of drainage systems, and existence of Miocene formations are among the causes of land degradation.