فصلنامه حفاظت منابع آب و خاک
سال پنجم شماره 4 (پیاپی 20، تابستان 1395)

The Urmia lake is the largest and the most important lake in Iran and is one of the most valuable international hemispherical resources in the world. But the Lake has been gradually getting dried nowadays. If the Lake gets completely dried, irreparable environmental, economical, and social damages will be done in the region. So, finding a practical solution for saving the Urmia lake is crucial. In the present research, it has been tried to predict the inflows of the rivers leading to the Urmia lake, once based on the long term period’s recorded data and another time based on the recent dry period’s recorded data, by using autoregressive moving average (ARMA) time series models in order to exert the effects of the recent drought in the forecasted data. The ARMA models are developed in the MATLAB software. After calibration of the created models, the predicted discharges of the basin’s rivers were entered into the simulation model of MODSIM in order to estimate the water consumptions in the basin's future condition and finally the entering flows to the Urmia Lake in each of two forecasting scenarios. Results show that in each of two forecasting scenarios of long and short periods, the environmental water right of the lake wouldn’t be supplied totally. Also, if the agricultural water consumptions are reduced about 14% and 56% in long and short periods respectively, the lake’s water right will be completely supplied. In this study, solutions for supplying the environmental water right of the lake are presented and analyzed.

Climate change causes changes in temperature and rainfall and consequently affects river discharge. Changes in rainfall can be simulated by global circulation models under different climatic scenarios but investigations of changes in river discharge require rainfall-runoff models. The Galikesh basin as one of most flood-prone basins in Gloestan Province is considered for determination of changes in river discharge under climate change effect. Temperature and rainfall is produced for future climatic period (2011-2030) based on global circulation model HADCM3, using LARS-WG data generator model. The produced data under different climatic scenario are used as inputs of calibrated IHACRES model to simulate river discharge for future climatic periods. The climate change analysis shows that under different scenarios in the study area air temperature in different months increases, but the annual precipitation decreases. The Mann-Kendall test is used to detect monotonic trend of seasonal and semiannual river discharge series. The results show no trend for spring and first half of the year and a negative trend for other seasons and second half series in 5 percent significance level.

In order to investigate the effect of detention reservoirs on flood in Jafar Abad basin, Golestan province, Iran, the precipitation-run off process as well as reservoir routing were simulated by HEC-HMS Software. The model was run under four different scenarios (without reservoir, with reservoir, half-full, and full) and for different return periods from 2 to 100 years. The statistical analysis of the results was done based on one way analysis of variance. To study the effect of reservoirs, two indices including the Flood Attenuation Rate (FAR) and StorageRatio (SR) were used. The results indicated that construction of detention reservoirs leads to postponing the incidence of the peak discharge and decreased peak discharge along with the volume of the flood leaving the reservoir, but these decreases were not significant. The influence of the reservoir diminished with the prolongation of the return period. The maximum levels of flood volume reduction for the empty, half-full, and full reservoirs were 61.1, 33.2, and 0.8%, respectively, and for the peak discharge were 63.9, 32.8, and 6.6%, respectively. The maximum value of FAR for the reservoirs under empty, half-full, and full conditions were 26, 19, and 7%, respectively. Similarly, the maximum SRs for the empty and half-full reservoirs were 14 and 5, respectively that showed the efficiency of reservoirs in controlling flood. The results demonstrated that the efficiency of reservoirs in flood control is not merely dependent on the reservoir volume and the amount of flood.

Agricultural sector is the largest consumer of water in the country. Therefore, offering comprehensive methods of water resources management and planning the right policies in order to increase water productivity in this sector seems to be necessary. For this purpose, in the present study an economic modeling inclusive of Positive Mathematical Programming (PMP) and the approach of Maximum Entropy (ME) to assess the impacts of irrigation water pricing policy on the management of water demand in Ardalan plain was used. The required data are related to the agronomical year 2013. The results showed that absolute value of demand price elasticity for alfalfa and tomatoes that have a higher water requirement is more than other selected products and farmer's demand for water in the production of these products is more elasticity. In addition, the results showed that increasing the price of irrigation water (under scenarios of 200 to 1000 rials compared to the condition of base year) leads to the reduction of the area of irrigated wheat, alfalfa, tomato and sunflower and increase in the area of irrigated barley and watermelon in the cropping pattern of the region. Also, applying this policy leads to the reduction of consumption water in the cropping pattern from 2.04 to 7.83 percent and the reduction of farmer's gross profit from 1.96 to 7.65 percent in Ardalan plain. Finally, applying the irrigation water pricing policy and using the cropping pattern change strategy along with it was recommended to reduce the demand of irrigation water and sustainability of water resources in Ardalan plain.

Landslide is one of the most important factors in agricultural land degradation of Taleghan watershed. Landslide is a type of mass movement causing land degradation, accelerating soil erosion and delivering sediments to Taleghan dam, annually. Landslide susceptibility mapping is the first step for landslide hazard assessment and mitigation. The main aim of this study has been the landslide susceptibility mapping in order to identify areas prone to this phenomena and controlling land degradation in Taleghan watershed. For this purpose, thematic maps of effective factors on landslide, including elevation, slope angle, slope direction, slope shape, mean annual precipitation, mean annual temperature, lithology, land-use, vegetation density, distance from faults, distance from streams and distance from roads, are prepared by using geographical information system (GIS), topographic maps, satellite images and field survey. These factors were analyzed using multiple regression method to prepare the landslide susceptibility maps. The results showed that about 26 percent of watershed lands have been situated in high and very high susceptible areas most of which are in lithology gy2 classification (consisting of marl with high gypsum and salt), have rain-fed land-use and are located at 0-500 meter distances from the faults.

More than two thirds of Iran is located in arid and semi-arid regions facing water shortages challenges. This emphasizes the need to reduce water consumption and the use of other unconventional water resources. Based on this fact, the present study deals with the effect of sewage and wastewater on some vegetative traits of Nitraria schuberi as a species adapted to arid and semiarid areas. Its design was a split plot design with six replications in desert Research Station, Segzy plain, Isfahan. In this study, irrigation with wastewater treatment at five levels ( 0 , 25 , 50 , 75 and 100 % ) , sludge at two levels ( presence or absence of sludge ) and two soil types (agronomical soil and Segzy plain soil) were used and morphological characteristic analyses of the plant using a SPSS software was done. Results showed that the highest rate of increase in height and canopy, basal diameter and canopy in Segzy plain soil is in 100% sludge and non- sludge treatments, whereas the same increase is for agronomical soil in sludge treatment with 100% Sludge and non- sludge treatments for plant height of wastewater level of 50%, basal diameter level of 100% and canopy cover of 75%. level for height, basal area and canopy diameter was 100, 50 and75%, respectively. The results showed that the lowest height, basal diameter and canopy cover for Segzy soil under non-sludge treatment for height, basal diameter and canopy cover was 0, 25 and 25%. Also, as for soils under non-sludge treatment for height, basal diameter and canopy cover wastewater levels were 0, 25 and 50% respectively, and for sludge application treatment 75% for basal diameter and 0% height and canopy cover, respectively.

Leaching of soluble salts from soil profile could be done as the most appropriate method to emend and reclaim saline and sodic soils. Determination of appropriate depth of leaching water to reclaim this type of soils for optimal management of water and soil resources seems to be necessary. For this reason in this study three different leaching methods including continuous ponding, intermittent ponding and sprayer leaching have been performed on saline and sodic soils in Veis area, Khuzistan. This evaluation was performed as an experiment on natural and intact soil columns with 1 meter height and 15 cm diameter (by pushing polyethylene pipe from upper part of excavated profile wall to the lower part vertically). Soil columns with primary salinity average of 14.13 dS/m, four layers 25 cm thick with clay loam and loam texture, and silt loam texture for the last two layers (from top to bottom) were used. Soil columns were treated with Karun of river water feed canal with 2.86 dS/m salinity in four different depths including 25, 50, 75 and 100 cm during experiment. Which was transferred through canals after each treatment of leaching depths, the columns were removed from leaching. At the end, experimental model was presented for each leaching method. . Exponential model in continuous ponding method was considered as the best model based on better correlation coefficient and lowestandard error. However, intermittent ponding method showed lower water consumption for soil desalinization and better leaching efficiency coefficient corresponding to soil texture of the area. Due to the shortage of water in the present condition and considering the leaching efficiency coefficient which is between 0.33 and 0.35 in different consecutive soil layers from top to bottom, intermittent ponding method will be appropriate for the studied area.