مجله سامانه های سطوح آبگیر باران
سال هفتم شماره 2 (پیاپی 21، تابستان 1398)

Khorasan Province is one of the areas in which it is not possible to cultivate farmlands because of low rainfall, and hence, flood farms (bandsar in local dialect) are considered an effective traditional method for flood cultivation in the region. We used a geological map of Birjand at a scale of 1: 250,000 to select the study area. This area includes the city of Birjand and numerous population centers such as Sarbisheh, Dastgerd, Hajiabad, Morak, Naferest, Giv, Mazhan, Khosf, Berming, Sarchah Shour, and Sahl Abad. In this research, based on the diversity of geological formations, the degrees of erodibility and the type of sediment load produced by each rock unit were determined. Then, appropriate areas for the development of bandars were located based on the quantitative and qualitative role of geological formations. Based on the processing of Google Earth images from the study area, the area covered by bandsars in ​​the region was calculated to be 24,000 hectares. The plains and alluvial fans of the region, which are potential locations to develop flood farms, are estimated at 658222.2 hectares, covering about 42.07% of the total area. By comparing these figures, it is estimated that only 3.65% of alluvial fans and plains in the region have been under construction and utilization for bandsars. The rock units were classified into appropriate, semi-appropriate, inappropriate and very inappropriate based on the severity of erodibility and the type of sediment load produced. Based on the results, it can be concluded that more than 75% of the formations in the upstream areas have poor potential and only 25% of the remaining districts have the potential for establishment of bandsars. Therefore, considering geology and other factors such as slope and occurrence of flood waters, it is necessary to take comprehensive measures to determine areas suitable for development of bandsars.

Knowledge about optimizing use of rain water under different systems is crucial for overcoming water stress and maximizing crop yield. In this regard, rain-water harvesting is one option that increases the amount of water per unit cropping area, reduces drought, and enables use of run-off. In this study, the importance of filters in rainwater catchment systems for increasing crop yields on steep lands of Khosbijan Natural Resources Research Station was investigated. Rain Water Catchment (RWC) systems with two treatments including: eliminating vegetation and pebble with a gravel filter, and eliminating vegetation and pebble without a gravel filter were created in almond seedling pits. Each year collar diameter, height, and canopy cover were measured at the end of the growing season. The results showed that over a three-year period, the changes in collar diameter, height and canopy cover were greater for filter treated plants. In other words, the presence of filters increased soil moisture storage in the root zone of the plant.

Soil productivity decline caused by inappropriate land use and human factors is the main threat to the functioning of soil resources and ecosystems in different regions of Iran, especially in Kermanshah Province. This research was designed to evaluate the effectiveness almond cultivation with a surface and subsurface harvesting system in improving soil permeability and inhibition of soil erosion in the Razin watershed of Kermanshah province. To this aim, after selecting the study area, some diagnostic features including the soil quality indexes, soil permeability, and soil erosion conditions were measured by field and laboratory methods in the study area and the control area. The results showed that, in the long term, the construction of orchards was able to eradicate all forms of soil degradation. The establishment of new orchards had an inhibitory effect on all forms of erosion, reducing surface erosion by 7.42 tons/hectare and increasing soil permeability by 15 percent. Also, while improving the soil physicochemical properties, the organic carbon content of soil increased by 30 to 118 percent, depending on the stage of establishment.

The aims of this project was to assess the capability of SWAT model and SWAT-CUP software in hydrological simulation and to evaluate the uncertainty of SWAT model in estimating runoff in arid and semi-arid watersheds. Model calibration and uncertainty analysis were performed using the Sequential Uncertainty Fitting (SUFI2) algorithm. In the stage of calibration and validation of water flow, performance of SWAT model was evaluated using R2, bR2 and NS coefficients between observed and simulated records. Based on the results, R2, bR2 and NS were estimated to be respectively 0.75, 0.59 and 0.67 in the calibration stage, and 0.46, 0.24 and 0.42 in the validation stage. The results showed that the performance of the model is weak during calibration. Also output of the model is acceptable but performance is not significantly high in general. The most important reasons behind the poor accuracy are lack of data on water diversion for agriculture, irrigation use, and cropping pattern within the watershed.

The managed recharge of groundwater is a stable and newfound technique which has already produced successful results and is expected to solve many of the problems of water resources, particularly in arid and semiarid areas. Artificial recharge of aquifers is considered as a strategy for the improvement of groundwater resources and their storage capacity to compensate for the damages inflicted on them. In Iran, funds are annually allocated to artificial recharge projects. Assessing the effects of these projects on aquifers is important, since positive results can expand the implementation of these projects. This investigation was carried out in the Lavar-e- Fin plains. The aim of this study was to evaluate the effects of a dam on groundwater. We estimated groundwater level before and after construction of an earthen dam. We used library data, data collected by the Ministry of Energy and information recorded during fieldwork. We used water level data from 6 piezometric wells drilled by Regional Water Company of Hormozgan Province and monthly precipitation data during the period from 1995 to 2015. All piezometric wells were located downstream of the dam. The effect of the earthen dam on groundwater level changes were analyzed over a 20-year period and for before and after construction of the dam. The general trend of groundwater level and water level changes in each piezometer well was descending, despite the positive influence of the earthen dam. The results showed that the dam lowered the rate of water level drop. The average precipitation in the 9 years prior to the construction of the dam was 182 mm, while the average rainfall in the next 11 years was 155 mm. In general, the results of this study showed that in spite of the recent droughts and increased uptake of groundwater, Laver dam has had a positive effect on the water level of the aquifer. Although the dam has not been able to compensate for all the losses due to overharvesting, it has reduced the severity of the decline to a large extent.

One of the most important componenets of water management in farms is estimating crops’ exact amount of  evapotranspiration (water need). The FAO-Penman-Montheis (FPM) method is a standard method to evaluate other techniques which are used for easy calculation of potential evapotranspiration, when lysimeter datasheets are not available. This study was carried out based on 18 years’ climatic data of Birjand (1998-2016), to determine the best experimental method based on coefficient of evaporation pan amongst methods proposed by Cuenica, Allen and Pruitt, Snyder and Orang. Then, the results were compared with the FPM method. The best method was used to assess the capabilities of gene expression method for prediction of daily coefficient of evaporation pan, which was the major goal of this study. The best equation for calculation of daily coefficient of evaporation pan was determined using these statistical factors: coefficient of determination, root mean squared error, mean absolute error, and percent error. The results showed that in Birjand’s climatic conditions, it is best to use the equation of generated by the gene expression method with a coefficient of determination of 0.77 and mean squared error of 0.021 millimeter per day.