مجله علوم و مهندسی آبخیزداری ایران
پیاپی 29 (تابستان 1394)

This study aimed to identify factors affecting the development of gullies and identify the most effective factor and the impact of each factor on the development of gully and gully development predictive models was defined in some regions of Kerman province. At first، 11 gullies in the regions of Baft، Rayen and Rabor are selected and the annual rainfall، width، length، slope bottom of gully، slope of area، the drainage area of gully، soil texture، pH، EC and silicate minerals were measured from the soil layers in the forehead gullies each year. Information obtained for both linear and volumetric expansion mode was analyzed by the SPSS11 software and statistical method regression. It was clear that soil salinity، silt soil، the average width of the gully، gully and slope of the watershed area have the greatest impact on the development of gullies in these areas. Also models showed that the affected factors on gullies development are surface runoff and erosion of soil that have generally occurred because of the effect of land use changes.

Rainfall intensity is one of the most important factors in soil erosion. Variation of the rainfall intensity during a storm event which is defined as temporal distribution pattern of rainfall may affect temporal variation of runoff and soil erosion. This is an essential problem to accurately estimate rainfall erosivity particularly in semi-arid regions، where various patterns of temporal rainfall distribution occurs during a In this study، eleven non-uniform temporal distribution patterns with basic intensity of 20 mm. h-1. maximum 5-min intensity of 40 mm. h-1 along with an uniform temporal distribution pattern with 20 mm. h-1 in intensity were investigated at twelve erosion plots (60 cm  80 cm) installed in a hillslope with 9% slope in 2012. Each plot was exposed to five simulated rainfalls. There were significant differences among temporal distribution patterns in runoff and soil loss. These differences were associated with soil surface breakdown and declining infiltration rate during peak rainfall intensity period. In the intermediate rainfalls، which the maximum intensity occurred at the middle time during rainstorm، there was the highest value of runoff (1. 39 mm) and soil loss (30. 31 g. m-2). In these storms، soil was slowly disrupted and wetted by raindrops at early times during the rainfall. However، when rainfall intensity increased، runoff and soil loss remarkably increased and this condition was approximately constant over time. In the advanced rainfalls، amount of runoff and soil loss were 98. 51% and 98. 63% as compared to the delayed rainfalls. In the delayed rainstorms، although rainfall intensity severely increased at the final periods during the event، the lowest runoff and soil loss occurred because the duration of the maximum intensity was relatively short and the rainfall was immediately stopped.

Identification of hydraulic parameters of aquifers is necessary for managing them. Pumping test is the most common way to measure these parameters that is very costly and time consuming. Vertical electrical sounding method is used to determine some characteristics of aquifers. The study area is part of Gol-E-Gohar iron ore deposit. This area is heavily faulted and the lithology is highly heterogeneous and numerous combinations of clay and marl are present in this area. In this paper، geoelectric data was used to estimate transmissivity (T) in the areas that do not have any available pumping test. To achieve this goal، the correlation between transmissivity and transverse resistivity in the areas with pumping well was obtained. Also transmissivity (T) was calculated using the Kozeny –Archie equations and Ohm''s– Darcy''s laws and were compared with estimated values obtained with the transverse resistivity. Finally، it was shown that the estimated transmissivity using transverse resistivity is more accurate than the porosity estimation method.

The first step to reduce the flood risk is flood control at the upper parts of watershed. So it is necessary to identify the flood prone regions within watershed، because performing the treatment activities at all over the watershed is impossible due to high expansion of the catchments. In this study، the potential map of flooding was prepared using SCS and overlaying data in GIS. The results showed that the coefficient of flood maintenance is low and the risk of flood occurrence is high due to characteristics of land use and soil hydrological units and the high weighted curve number equal to 78. The flooding potential map indicated that the risk of flood occurrence is really high، especially at the margins of north regions and upper parts of watershed duo to unsuitable land use type، high slope and outcrops without vegetation cover. Therefore، the priority of such regions for watershed engineering operations is more than other parts of watershed. The results of HEC-HMS model has also showed that fifth-sub catchment has the first flood control priority because of the high slope and CN number of 89.

Due to the importance of water in sustainable development، water resources co-management is one of the basic strategies for obtaining sustainable management. In recent years، the application of social network analysis is regarded as a new approach in water co-management. In this study، structural analysis of the social relations among local beneficiaries has been studied in Boolan village located in Razin watershed of Kermanshah city. It is used the social network analysis approach as method with emphasis on trust and collaboration ties and quantitative and mathematical indicators on the macro-level of local beneficiaries network (Density، Centralization and Reciprocity). The results showed that the level of social cohesion is medium and poor based on trust and collaboration matrixes. Also the level of social capital in the village has been measured about middle to poor. The degree of reciprocity indicator is medium for trust and collaboration ties، so the stability of network is medium. Also the level of correlation between trust and collaboration is 57 percent. Based on the results، it can be concluded that amplification trust and social participation in this village to speed up the flow of information and resources، as well as an increase in unity among beneficiaries are necessary. So that we can reduce time of the implementation water resource co-management and to succeed in this field.

One of the most important types of water erosion is gully erosion. This type of erosion causes remarkable changes in lands، production of abundant sediment and deleterious social and economic consequences; especially in arid and semi arid regions of the world. Threshold is the point after which the behavior of the system changes and it can be related to the internal or the external factors of the system. One of the important questions about gullies is that in what condition the threshold of gully is created and expanded. Identifying the conditions seems important considering the fact that it is possible to compare conditions of the threshold with the regional conditions and determine how much the conditions are close to thresholds of gully creation and or Expansion. For this purpose، the current research aims to determine threshold of effective factors on length expansion of gullies in Mahourmilati region in south-west of Fars province by using the data mining techniques. The findings of the current research which were achieved by modeling based on K-Means Clustering Algorithms and CART Decision Tree and in Clementine software (version: 12. 0) indicated that the length expansion of gullies in the studied region is the function of SAR، soil acidity (pH)، and output area. To improve the soil of the studied region، it is recommended to consider improvements، revegetation and enhancement of soil organic matters prior to effective actions in controlling the length expansion of the gullies.

Nowadays، due to water resources scarcity (especially in arid regions)، groundwater resource quality and quantity management is essential. In this research، spatial variations of chemical characteristics of groundwater such as EC، Na، Mg، Ca، HCO3، TH and TDS were investigated in one-year period (2010-11) based on the data collected from 42 deep wells of Yazd-Ardakan Plain. In order to prepare zonation characteristics of water quality، Simple kriging was used. The results showed that the fitted model to the variogram of Ca، TDS and EC are Gaussian. Homogeneity of variogram model of these three parameters can be considered due to positive، significant and strong correlation between them and the same spatial variation in aquifer. Best Model variogram for Na، Mg، HCO3، TH is spherical. Effective range of investigated indices was approximately obtained between 5 to 104 kilometers. Effective range of EC، TDS and TH and the effective range of Na and HCO3 were very similar in the plain. RMSE criteria was obtained less than 40 percent for all indices that shows the accuracy of estimates. Agreement of correlation between the observations and the maps showed good accuracy of variogram model and Simple kriging method for zonation of characteristics of ground water quality in Yazd-Ardakan plain.

Flood is one of the phenomena in different regions of the world and our country that cause financial losses each year. In Programs to deal with floods، flood zoning are one of the non-structural prevention solutions that the economic justification is higher. In this study، parts of the flood areas in Chardavol River (Chenare reach) at different return periods are evaluated. First، statistics and information hydrological such as discharge was collected from Regional Water Organization of Ilam. Then after testing a run test and Kendal test، uniformity and randomness of the data was confirmed. Then using the average daily discharges at hydrometric station، by using SMADA software، the different distributions of the observed and been completed data was fitted and 3 Parameter log normal as the best distribution of data was determined. Then after making the field operations، river reach with 1. 5 km length was selected. Then preparation of river TIN From digital mode، by using the extension HEC-GeoRAS، 50 cross section created on the TIN and introduced to the model. Finally، performing a series of procedures and specific operations، maps flood zoning in the 5، 25، 50، 100 and 200 returns period is provided. The results of this study showed that flood risk marginal lands because of the wide channel bed in most areas are relatively low. This event in floods with high return periods is observed

Soil erosion on agricultural land is a main problem and constitutes a threat to soil quality and agricultural production. Preparation of a risk map is needed as a prerequisite for control of soil erosion and planning of environmental projects. This study was conducted to assess the risk of soil erosion by mapping and zonation of soil erosion risk in farmland of Tehran province and determine their extents. The map of soil erosion risk was prepared with four classes (low، moderate، high، and very high); by integration of slope gradients، land use، and erosivity map using Geographical Information System. Results showed that the area of Tehran province farmland is 320887 ha (17. 05% of total area). 4478 ha of farmlands are located in areas with slopes more than permitted slope for cultivation، that 3121 ha of them have rainfalls with high and very high erosivity. In general، 98. 1، 0. 5، 0. 4، and 0. 97% of farmlands have the low، moderate، high، and very high erosion risk، respectively. Soil erosion and land degradation are occurred due to crop production activities in the areas with high and very high erosion risks (4478 ha of farmland). Therefore، in these areas، special soil conservation and land management should be conducted، otherwise، the land use of these areas are necessary to changed to grassland، garden، and artificial forests.