reclamation of a sandy desert through floodwater spreading: ii. characterization of clay minerals in the watershed and the freshly-laid sediment

the artificial recharge of groundwater (arg), where practicable, is an easy and economical method for desertification control in the arid and semi-arid zones where overpumping has critically lowered the watertable. although desiltation of floodwaters, which is a prerequisite for the arg, leads to rehabilitation of the eroded sites that house the sedimentation basins (sbs), the gradual impermeability of these basins and infiltration ponds by migrating phyllosilicates shortens the economic life of such projects. therefore, characterization of these minerals is necessary if treatments for their removal are to be found. as soil erosion in the watershed that supplies the arg systems with floodwater deteriorates the land, and threatens the recharge facilities and other hydraulic structures downstream with siltation, identification of the erosion source facilitates prioritization of soil conservation activities. clay mineralogical analysis has been developed in recent years as a powerful tool in sediment source attribution. however, applicability of such methods to cases in iran requires regional studies. sediment samples were collected at 0-10,10-20, and 20-30 cm increments on two transects in the 1st, 4th and 6th sbs in a gareh bygone plain arg system. rock samples were collected on the southern flank of the bisheh zard basin that supplies floodwater to the arg systems. all samples were characterized by the xrd method. transmission--electron micrograph (tem) of one sample was also obtained. chlorite, mica, smectite, and possibly kaolinite were detected in all samples. the presence of palygorskite was revealed only in a tem. the non - clay minerals were calcite, dolomite, alkali and plagioclase feldspars, gypsum, halite and quartz. the common origin of these inherited clay minerals precludes their utility in sediment source detection.