Investigation on the Methods of Rehabilitation and Development of impaired Watersheds (1994-1999)

Innovation of different methods to overcome the environmental problems has always been a challenge to human being. Progress in agriculture by providing water and other inventions according to the needs, shows that the mankind puts much effort for his survival. Iran is regarded as an arid or semi-arid country low precipitation, irregular distribution of rainfall in time and low soil fertility are'the problems-of'rehabilitation and extension of cultivated .and pasture lands . Improper use of resources without the knowledge of science and technology has increased the related problems. Therefore, the destruction of cultivated lands has hampered the production of crop plants and has brought about the problem of flood ¬water and its sediments. The amount of sediments in Iran is about two milliard tons, which contain the 11 % of the total sediments in the world (18 milliard tons). This indicates the magnitude of , land degradation in our country. Therefore, to overcome these problems and reduce the damages imposed to natural resources, watershed management science has been developed. The research programs of rehabilitation of destructed watersheds have been proposed to use the potentials of Khajeh area properly. The aims were as follows: 1. Develop ment methods of rehabilitation of destructed watersheds via the use of technological, mechanical, and biological measures. 2. Quantitative evaluation of effect of watershed management to improve the --- __ .cualitv of.nmoff water nhvsicallv and chemically in destructed watersheds. 3. Optimize the utilization of water and soil resources in destructed watersheds and introduce the most proper scientific techniques. In this program, complementary studies. in the station have also been managed in addition to-general-:-study-of- Aji-chai region and- its geology, soildevelopmentand hydrology. Basic studies in the station, resulted in the choice of proper rehabilitation methods with the following goals: 1. Prevention of soil erosion. 2. Soil conservation and regulation of water status in the region. 3. Rehabilitation of the study area by the fast coverage of the soil with plants. 4. Increase the income of the people in the area. To achieve the above "mentioned targets, several measures such as band contours), trench contours, catchments basins, pools to store runoff and sediments, planting trees and shrubs resistant to salinity and rehabilitation of green cover via planting pistachia atlantica, pistachia vera (instead of Hippophae, Atriplex, Famartix l Halloxylon, Zygo phyllum, and forage plants such as" Agropyron elongatum , Aeluropus were considered in the region to recognize the proper method of rehabilitation. Although some preliminary data have been obtained, but the number of years is not enough to have a strong recommendation. Therefore the experimentation is needed to be continued for a second cycle of 4 years. On the whole the following conclusions could ;'l5"e'made on the basis of the preliminary data. 1. The pastures of the area were poor , but after 4 years they could be rated as iritermediate with a grade of 39. The pastures trend are positive since the biomass production has raised from 200 up to 553. 75 kg/ha, where as in the similar untreated pasture no positive changes was observed. Also the density of palatable plants such as Agropyron elongatum, Aeloropus, Trigonella, Bromus japanicus have increased in the experimental area. 2. The pistachio acquired high rate of survival and its growth rate per year was 35 cm. - Pistachia atlantica was medium in % survial and its growth rate was slow. - Atriplex canescens had 2. good survival rate with a 66 em growth per year. 3. Changes of soil fertility in 3 years with several experiments was marked that association coefficient between PH and Ec and "So on is low that is repersentative several changes in soil profile and is as positive random of worked projects. 4. Some chemical changes has been observed in underground water, but the data obtained isnot enough to reach for a conclusion. 5. There is no surface runoff and flood water in the experimental area and some water has been gathered behind the bands in trench contours and behind the bands and wells for a proper utilization. On the other hand, in the untreated area the land destruction is still observed. 6. Band contours, trench contours, pools to store sediments and runoff were efficient to control runoff and sediments, These measures resulted in reclamation of soil and degraded lands. - 7. The Ec of runoff gathered behind bands and contours ranged 1-1.7 ms/cm while the Ec from control basin was 4-7 ms/cm. 8. The recorded TDS from flood water in untreated area is about 230-250 gr/lit, while in the experimental site is very low (50 grllit). 9. The EC of wells from untreated area was greater than 20 ms/cm and the water is of poor quality compared to water gathered from surface runoffs and bands. Therefore the salinity of Aji-chai river is possibly influenced from underground waters.