Journal of Range and Watershed Managment

Abstract Abstract

Precipitation plays an important role in climatic, water, energy and biogeochemical cycles. Several global and regional data sets currently provide historical estimates of this variable over Iran, including the MWEP and WFDEI forcing datasets and production of some institutions such as MOHC, SMHI and IITM. All these datasets provide data with different resolutions based on gage stations, satellite Images and models output. In this study, we do an inter comparison between these data sets during 1990- 2008. We also validate all ten data sets against independent ground station observations over 30 second-order basins of Iran. MSWEP and WFDEI have an acceptable compatibility with observational data on different spatial and temporal resolutions. RMSE and Bias are 5.68, 6.34 and 0.58, 2.75 for these two datasets during 228 months, respectively. However, it is needed that MSWEP improves in the western and northwestern parts of the country and WFDEI in June and September months. Our findings in this research provide valuable guidance for a variety of stakeholders, including rainfall- runoff and land-surface modelers, watershed management studies and data providers.

Abstract Gamasiab River is one of the five main branches of the Karkheh River and plays a basic role in preserving the life and ecosystem of the region. The first step in the adoption of proper and sustainable methods for managing the water resources of the Gamasiyab river is to gain continuous knowledge of the quantitative and qualitative status of the water as well as its variations. The use of hydrological models is common to simulate quantitative and qualitative processes associated with the water cycle. One of the models that is widely used in the international level is the SWAT model. In this research, we evaluated the efficiency of SWAT model in simulation of Gamasiyab river flow. For running this model requires a DEM, soil map, land use map and slope classification. Initially, discharge data in daily step at Polchehr Hydrometric Station was calibration (1977-1995 AD) and then validation (1996-2005 AD) by using precipitation data of two synoptic stations and three weather stations and minimum and maximum temperature of two synoptic stations. Statistical coefficients including Nash-Sutcliff coefficient, R2, P-factor and R-factor for calibration period were 0.71, 0.73, 0.79, 1.36 respectively and for validation period were 0.57, 0.61, 0.71 and 1.34 respectively. These results indicate that the SWAT model has the ability to simulate the Gamasiyab River discharge and researchers can use this model to apply management scenarios in short time and low cost for better decision making.

Abstract landslides situation recognized using interpreting the aerial photos and extensive field measurements. Among total number of 200 identified landslides, %70 (140 landslides) of them have been utilized for model executing and %30 (60 landslides) of them for verification randomly. This research criteria including geomorphological parameters, hydrological parameters , geological parameters and environmental parameters . The Shannon’s entropy model have been used for defining the criteria weight and Area density model for defining classes weight, then the regionalization map obtained by combining the criteria and classes weight in ArcGIS 10.2 software environment and classified to 5 classes very little, little , moderate, high and very high according to natural fractures. The Roc curve have been used for model verification. The clerical accuracy results indicated that the compound model have the high accuracy 0.877 (87.7%) for identifying the regions susceptible to landslide. According to the results, slope length, slope and topography wetness index have had the most effect in occurring the landslide. Among total area of region (168547 hectar), 27.39% (46165.02 hectar) have been placed in high and very high sensitive. The prepared regionalization map can be useful for planning land use and building the infrastructure installations such as road.

Abstract The runoff simulation in a watershed provides insight on the processes affecting runoff generation and the stream flow characteristics like spatial and temporal variability of stream flow. This insight helps managers and planners in informed decision-makings on water resources management and planning. The objective of this study is to compare the performances of the complex SWAT model and the simple IHACRES model for simulating runoff in the Doiraj river basin, Ilam province. For this purpose, SWAT model due to having many parameters affecting stream flow and the use of GIS, and IHACRES model due to the low and easy access data requirements, are very practical. In this study, the data over a period from 1994 to 2004 and the statistical criteria of R², bR², and NS were used to evaluate performances of IHACRES and SWAT models. For IHACRES model, values of R², bR² and NS were estimated equal to 0.34, 0.112 and 0.33, respectively for calibration period and values of 0.47, 0.235 and 0.43, respectively for validation period. In addition, for SWAT model, the coefficients were estimated equal to 0.41, 0.314 and 0.12 respectively, for calibration period and values of 0.68, 0.632 and 0.56, respectively for validation period. Final results of this study showed higher performance of SWAT model relative to IHACRES model for simulating daily runoff in Doiraj river basin and can be used to simulate runoff in the watersheds with limited data and similar natural conditions.

Abstract Runoff and sediment measurement is difficult in mountain watershed because of many different problems such as time and financial limitations. So using simulation model is necessary in this regard. Accuracy and precision evaluation of models for different watershed of Iran is necessary. The aim of this study was the evaluation of SWAT model efficiency in simulation of runoff and sediment yield in Chelchay watershed in Golestan province, Iran and also calibration and validation of SWAT. SUFI2 algorithm was used for calibration and validation. Nash-Sutcliff for calibration period (2001-2005) and validation period (2006-2009) for average daily discharge was 0.5 and 0.4 respectively and for sediment concentration was 0.71 and 0.92 that is good according to past research results. Because SWAT is complex and integrated model and can be used as a management tool in watershed management so it is suggested that it would be used for evaluation of management activities effects in Chelchay watershed.