جستجوی مقالات مرتبط با کلیدواژه "uncertainty analysis" در نشریات گروه "آبخیزداری، بیابان، محیط زیست، مرتع"

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.

This paper describes the utilization of a system dynamics model to predict the effects of vegetation-based management scenarios on structural landscape ecology in the Hablehrud River Basin. The river basin covers an area between Tehran and Semnan provinces. In this research, vegetative management scenarios include: the current condition, terracing, saxaul plantation, riparian restoration, forage growing, bunch seeding, contour furrowing, tree plantation, grazing exclusion, seeding, drill seeding, orchard development, and agroforestry. In order to predict the effects, Weighted Mean Patch Size index (WMPSI), Weighted Land Cover Area Index (WLCAI) and Riparian Proportion Index (RPI) were quantified. Additionally, the model uncertainty analysis was conducted using bootstrap method. Ecological impacts of the scenarios using aforementioned indices were predicted and the best scenarios were chosen using system dynamics. Results suggest that considering WMPSI, tree plantation and riparian restoration scenarios are the preferred scenarios. Seeding and orchard development scenarios were considered to be the best scenarios based on WLCAI. Moreover, riparian restoration and saxaul plantation were chosen as the best scenarios considering RPI. Seeding and riparian restoration scenarios obtained the highest priority considering the combination of the indices. WLCAI and RPI have the minimum and maximum uncertainty levels with respect to coefficient of variation as 0.28 and 0.45, respectively. The system dynamics models are capable of predicting the effects of various management scenarios providing the information required for decision making and management at watershed scales.

The phenomenon of sedimentation in dam reservoirs is the most important threatening factor in huge investment of capitals in hydraulic projects. Uncertainty analysis for each phenomenon shows the real view of its parameters and creates real understanding of the effective factors on the phenomenon. In this research, to estimate the volume of sediments in reservoir, using hydrometric and sediment data of Karaj River from 1961 to 2003, factors affecting sediment transportation and a model considering non-uniform sediment sizes. Then by using Monte Carlo simulation method and statistical input parameters, effective factors on sediment volume in reservoir, random input parameters and Latin square sampling method, some samples were obtained. At the end, the uncertainty of each parameter was introduced using statistical characteristics. The Results from uncertainty of annual sediment of reservoirs, expressed as coefficient of variations, was introduced as 56% Sensitivity analysis showed that annual mean flow rate and sediment rate were the most important factors in estimation of reservoir sediment volume.