فصلنامه حفاظت منابع آب و خاک
سال هشتم شماره 2 (پیاپی 30، زمستان 1397)

Sensitivity analysis of reference crop evapotranspiration (ET0) is crucial for improving water management in the arid and semi-arid country as like Iran. However, it is important to analyze the sensitivity of ET0 to meteorological parameters, since the climate globally has been changed to some extent. In this study, sensitivity of ET0 by varying the climatic parameters at 36 selected stations in the West and Northwest of Iran was investigated. The priority and effect of the climatic parameters in different months at the selected stations were found by sensitivity analysis. The ET0 is calculated based on the most recommended form of the FAO-56 Penman-Monteith method. To analysis the sensitivity, variations of ET0 depends on the changes in minimum temperature (Tmin), maximum temperature (Tmax), wind speed (u2), minimum relative humidity (RHmin) and maximum relative humidity (RHmax), in the range of ±20% with the step of 5% was calculated. Finally, the parameter with higher importance for each station was obtained. Results showed that ET0 was more sensitive to the variation of Tmax at the 13 stations (36.11%) in annual time scale. The maximum change of ET0 by increasing of Tmax with+20% was found at Ardebil (15.54%) and the minimum change in the same situation was found to be 6.05 % at Meshkinshahr. The range of the changes by varying T min was between -47 % (in Sanandaj) to 0.91 % (in Khalkhal).

The AquaCrop model is a powerful tool for the simulation of crop response to the different quantitative and qualitative management of irrigation that advanced by FAO. In this study, the latest version of this model (v. 6) was evaluated for simulating sunflower yield, water productivity and soil salinity under different irrigation management using saline water. Field data were collected in order to calibration and validation of model during two crop years (2014 and 2015). The experiment was conducted as a factorial design in completely randomized blocks including two factors: the quantitative irrigation management in two levels (full irrigation and partial root zone drying irrigation in 75%) and the qualitative irrigation management in three levels (non-saline water, saline water and non-saline and saline water alternation), with three replications. While a significant reduction of 3.1-32% in grain yield were observed under water-saving irrigation treatments compared to FI (4706.7 and 4367.2 kg ha-1 in 2014 and 2015, respectively), the PRD1 treatment resulted in a slight reduction of 3.1% and 5% in grain yield, in 2014 and 2015, respectively. FI had the highest WPET (0.90 and 0.89 kg m-3 in 2014 and 2015, respectively), and PRD1, PRD3, FSI, SI and PRD2 treatments ranked next. Sensitive analysis result showed that the model sensitivity to the volumetric soil water content at soil saturation and field capacity point, maximum canopy cover, HIO, time to flowering, time to CCx and CGC is more than other input parameters.

The longitudinal dispersion coefficient from the perspective of public safety and human health, is one of the important parameters for predicting and characterizing the transport of pollution in rivers and shallow waters. This paper aimed at investigating the efficiency of the classical advection- dispersion Equation for predicting transport of pollution in a gravel bed rivers. Some tracer experiments were done in a flume with longitudinal slopes of (S= 0.001, 0.007) and five discharges include of (7.5, 11.5, 15.5, 20.5, 25.5) lit/sec. Simulated (OTIS) and analytical breakthrough curves were compared with observed data. The results of this study indicated that advection- dispersion equation in prediction of tailing edge of breakthrough curve has less accuracy. So it not be used in rivers with storage area but it is very helpful to estimate initial value of longitudinal dispersion coefficient. The calculated dispersion coefficient increased with augmentation distance from the injection site. The domain of estimated dispersion coefficient for the tracer test of this research is between (0.0073- 0.18) m2/sec. the results of calculating travel time parameters from experimental BT curves showed an exponential relationship between them and the distance from the injection site. Finally, using a geometric, hydraulic, and tracer test data and applying a Buckinghamۥ π theorem a new equation was developed to predict the longitudinal dispersion coefficient. The relative error and normalized root mean square error for the proposed equation were calculated respectively 24% and 1.37.

Shallow landslide is one of the natural hazards that damage life and property of people in mountainous watershed. Due to the fact that a lot of landslides events have been occurred in this watershed, assessment the risk of shallow landslides by using appropriate methods and determine of effective factors in reduce the hazards of it is so effective. The potential of using maximum entropy modeling for landslide susceptibility mapping is investigated. In the case study of west of Ardabil province, 74 landslide occurrences were identified, 52 landslides (70%) used for training and the 22 landslides (30%) applied for validation purpose. environmental factors including continuous (altitude, slope, aspect, plan curvature, drainage density, and rainfall) and categorical (lithology and landuse) data were used as inputs for modeling. From the optimal setting test based on cross-validation, a continuous data and its combination with categorical data showed the best predictive performance. The results of validation showed that the ROC and AUC for success and prediction rate of model was 96.1 and 97.6%, respectively. Factor contribution analysis indicated that altitude and rainfall layers were the most influential factors. From interpretations on a response curve, steeply sloping areas that consisted of excessively covered with old alluvial terrace soils were very susceptible to landslides. Predictive performance of maximum entropy modeling was slightly better than that other models like of a logistic regression which has been used widely to assess landslide susceptibility. Therefore, Maximum entropy modeling is shown to be an effective prediction model for landslide susceptibility mapping.

Iran has a warm and dry climate and its annual rainfall is 250 millimeter.Therefore,in Iran with the low rainfalland its very unsuitable distribution, the effective use of modern technology to improve the use of water resources efficiency in limited water resources is vital.One of these solutions to protect and store moisture is the use of super absorbent and soil reformer.In this research,the effect three levels of zeolite(0,10and15weight percent)and four levels of superabsorbent geohumus(0,100,150,250gr) and irrigation(normal irrigation,low irrigation)on the vegetative properties of Nitraria schoberi in seedling cultivation on the field, as well as the effect of these materials on some properties of soil were investigated. In order to evaluate the effect of each factors including irrigation, type and level of superabsorbent addition on the studied characteristics, the data were analysis using SPSS-22 software and the data were analyzed according to the analysis of variance table and the mean comparison of the treatments was doneby Duncan's comparison test. The results showed that the use of superabsorbent in this study had a significant positive effect on growth indices of seedlings includingheight, large diameter, small diameter and collar diameter of Nitraria schoberi seedlings in comparison with control sample.The highest amount of vegetative indices by normal irrigation was respectively(60.22cm,67.33cm,13.88cm,6mm)andThe lowest amount was associated to, low irrigation treatment (control).In addition, the use of superabsorbent had a positive effect on some properties of the soil. In other words, the addition of the superabsorbent to the soil reduced the Electrical Conductivity(1/39dS/m), reducing the Bulk Density(1/46g/cm³)of the soil

The present study was proposed to evaluate severity of drought in Eghlid region where in Fars province. For this purpose, standardized water level index (SWI) and rainfall anomaly index (RAI) were used during a 10 years’ statistical wet period (1384 to 1393) by using monthly water table depth data of 107 pezometric wells and monthly precipitation data of 10 meteorological and synoptic stations. In order to resolve defects of precipitation data, using SPSS software, the correlation coefficient through stations was analyzed and restored with ratios approach method. For determining severity of drought both of data sets of drought indexes were calculated by Excel software in 3, 6, 12, 24 and 48 monthly periods. Five of the biggest occurred droughts were determined in each index and its mutual index and droughts zoning were accomplished using inverse distance weighted (IDW) in ArcGIS program. The results indicated that severity of droughts were increased in recent years. Furthermore, the results are implicating which there is a time delay between hydrological and meteoric drought indexes, in fact it was observed that by calculating the correlation coefficient between the indexes for south and west of Eghlid, the time delay is 2 to 4 years.

The main consumer of water resource in the country is agriculture sector – AS a result, the largest amount of water losses is related to this sector one of the most important processes of agricultural water losses related to real evapotranspiration because during the evapotranspiration process (ET) , a large volume of water of surface soil transferred transpiration ally and also sub soil water is transferred through the vegetation and real transpiration to the atmosphere. In this research using the algorithm SEBAL and MODIS indicator the real evapotranspiration rate was evaluated in Sodlaneh village of Quchan in 2011.Monthly results indicate the highest evapotranspiration was related to the months of April, June, May that with average of 17, 21, 26 mm was topped up respectively. High levels of evapotranspiration in spring due to land use map of the area which dominates annual evaporation and transpiration of the Sodlaneh village is calculation this year as 260mm that its Maximum equal with 644 mm is related to eastern part of the village (such as villages Dadanloo, Dizadiz) and and at least equivalent to 102mm is related to the central and western parts of the village (such as village of davoodli and dollo). The results of this study with the land data of Sodlaneh village shows that there is a significant correlation.

cropping pattern changes and increasing energy tariffs helps groundwater resources management. The aim of this investigation was to study the effect of crop pattern on groundwater level in Mehranplain using the system dynamics approach under different scenarios of energy price changes. To develop the model, a conceptual framwok was designed and the dynamic hypotheses were formulated. The calibration and validation of the model were performed for a period of 8 and 6 years, respectively, and the model simulated in a 25-year period until 1420 in nine scenarios. The results showed that changing the crop pattern from alfalfa to conola with increasing 100 percent in energy tariff would have the most positive impact on aquifer is equivalent to an increase of about 55 million cubic meters of aquifer water volume, and an increase of about 8 meters in the groundwater level. Also changing the crop pattern from alfalfa to corn with increasing 50 percent in energy tariff lead to groundwater level stability.

Soil moisture (SM) is the major factor controlling plant growth particularly in rainfed lands. It varies due to the change of climatic parameters such as precipitation and air temperature and evaporation. This study was conducted to found climatic factor influencing soil moisture under rainfed conditions. A field experiment with two cultivated conditions: under fallow and cultivated with winter wheat was designed in a rainfed land with 10% slope steepness in the University of Zanjan during growth period from 2016 to 2017. Toward this, six plant plots with 2m × 5m dimensions were installed along the slope orientation similar to conventional tillage method in the area. Volumetric soil moisture was measured in 7-day interval using TDR model IDRG SMS-T2 set during growth period Climatic variables including air temperature (AT) and precipitation (P) along with soil temperature (ST) were determined during growth period. Based on the results, SM in cultivated plots was about 11% less than the follow plots, and this difference was statistically significant between the two. Amount of soil moisture significantly varied among different months (p<0.001). Significant correlations were found between SM and P, AT and ST in the two cultivation conditions (p<0.05). Higher dependency of SM on AT (r=0.44) and ST (r=0.51) was observed in fallow plots as compared to planted plots. This study revealed that ST is the most effective property controlling SM in fallow and planted lands in the area.