WATERSHED ENGINEERING AND MANAGEMENT
Year:2017 | Volume:9 | Issue:1 |Papers Count:10

Annually, high amount of soil is washed out by erosion from the watershed. Implementation of appropriate management methods to control soil erosion is therefore essential. Application of economically-effective and environmentally friendly amendments to soil is one of the solutions and new technologies to control soil erosion. However, the comprehensive assessment of the impact of commonly used soil amendments on soil erosion has not been conducted. The present study therefore aimed to assess the performance of combined application of polyacrylamide powder (6 gm-2) and vermicompost (24 gm-2) in comparison with individual application of the polyacrylamide and vermicompost as well as control (without amendments) condition to control runoff and soil erosion under laboratory condition and on a clay-loamy soil. The study variables of runoff, soil loss and sediment concentrations were measured under a simulation rainfall intensity of 80 mm. h-1 and duration of 8 minutes. The results indicated a statistically significant effect (p=0. 00) of all study treatments on the reduction of runoff, soil loss and sediment concentration from the study small plots. The combined effect of polyacrylamide and vermicompost on runoff and sediment concentration was also found greater than that recorded for soil loss.

Underground aquifers are one of the main sources of water supply in most parts ofIranwhich are affected by natural and manmade factors in recent decades. Land and geological formations are from the natural factors in any region. In this study, the investigation of the quality of groundwater resources and their correlation with geology formations were considered. For this purpose, using the geological map of the area geological formations were extracted. Then, to determine the water brigade, the qualitative data of 76 operation wells and three control operation wells, were entered in the Chemistry software. Next, formations were classified according to the type of production and the effects of their dissolution (quality); in the next step, buffers in intervals of one, three, five, seven and 10 km were created around wells and their layers were overlaid with geological maps. The t-test results showed that at 95%, at one, three, five and seven km from the wells, the impact of formations is significant on operation wells, but, at a distance of 10 km and with increasing distance, this effect was less and significant effect there is not in this respect, but, their total impact of non-quaternary formations increases on the wells. Also, the results from Boulian logic showed that that formation (Qt2) has the most spreading near the wells, including alluvial fans and young alluvial sediments which are the original location for feeding aquifers. But, by increasing the distance from the wells, the impact of non-quaternary formations like Cretaceous limestone and Batholith rocks (volcanic) that have the ability to produce water Brigade of sodium chloride and carbonate increases.

Based on expert estimates, many Iranians believe that the amount of sediment yield is annually increasing. This study has attempted to assess the temporal trend in Suspended Sediment (SS) of Jajroud and Karaj rivers at Roudak and Sira stations. respectively with adequate data collected during four decades. The SS yield data and SS concentration as well as flow rate data were analyzed. Preliminary investigation showed that more than 92 percent of the SS at Roodak and Sira stations is transferred by top two and three flow deciles (equal to 20 and 30 percent) of the effective or flood discharges. Among these, the highest decile (10 percent) is responsible for carrying about 80 and 64 percent of SS accounted for the two study sites correspondingly. Therefore, mainly analyzing the highest decile flow data was considered. Four techniques were performed including: a) fitting regression lines to the measured SS concentrations and weights vs. time, and b) graphical comparisons of dependent variables (average discharge, average SS concentration and weight) during the four decades, c) using the Kruskal– Wallis test, and d) using Kendall rank correlation coefficient. All interpretation techniques showed decreasing trends vs. time which were significant based on the two nonparametric techniques. Since, the highest decile of daily flows of study sites have not shown any increasing trends during study period, it can be concluded that unlike the general publics’ believes the amount of SS has decreased. A possible explanation for this descending trend might be as a result of 43 and 25 conservation projects implemented during recent 30 years in the upstream basins of Amirkabir and Latian dams, respectively. The descending SS trend does not necessarily mean lower rates of erosion in these basins; but it rather means lesser sediment delivery ratios.

Self-similarity characteristic of climate variables provides the spatial and temporal analysis, using fractal dimension. Therefore, the application of fractal geometry in predicting the nature of many natural processes (e. g. rainfall) in several areas is of great importance. The purpose of this study is to determine and calculate the fractal dimension of wet and dry periods, interpret and evaluate the spatial characteristics of dry and wet periods over 40 rain gauge stations in Golestan Province. Toward this attempt, the box-counting method has been employed to determine the number of wet-dry months at one to nine months temporal scales and the calculation of fractal dimension. Then, the regression lines are used to estimate the corresponding fractal dimensions over rainy and non-rainy periods. As well as the severity and duration of wet-dry durations were presented over the study area. The results indicated that variations of rainy/non-rainy durations vary in a range of 11 percent. According to the results, the number of consecutive wet-dry months decreased in coarser time scales (months). The analysis of fractal dimension showed that the dry periods have a lower frequency. The fractal dimension values were considered to determine the variations of precipitation regime over studied stations. Also, the intensity of wet durations is higher in central and eastern parts of the study area, while the western part of the Golestan Province had experienced more persistent wet periods.

Assessing drought effects on water resources are important on optimizing water management activities in agriculture and natural resources sectors. The groundwater model can be used as a valuable tool in the management of groundwater resources. Therefore, investigation of ground water balance analysis affected by meteorological drought using mathematical models is applicable and important objectives in sustainable development of water resources and the environment. Tuyserkan is one of the most important plains in Hamadan province as the main source of water supply for the water wells usage in orchards and farms. The goal of this research is assessing the effects of metrological drought index on water balance changes using mathematical modeling by GMS software. For this purpose, after calculation of Standardized Precipitation Index and determination of wet and dry spells in the study area, and selection of three sample years as normal (1387), wet (1388) and dry (1389), the groundwater balance was analyzed in this three sample years. The normal year was used for calibration of the model and wet and dry years for validation of the GMS. The results showed that the GMS model can simulate groundwater level in normal, wet and dry year (error statistics are respectively 0. 73, 0. 85 and 0. 93). Comparison of meteorological and hydrological drought indices showed that meteorological drought cannot affect the groundwater level alone and excess use of exploitation wells has great influence on the groundwater table changes. Interestingly, the results showed that drought strongly influences water balance changes.

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.

One of the most important factors of soil erosion is the improper use of lands according to their potencial. According to sosio-economic factors of watershed, it is impossible to reduce the amount of soil erosion in the rate of natural erosion, but, it can be reduced, through integrated watershed management. Soil loss mitigation while having high productivity is possible by appropriate land use and land capability. In this research, Sheshtamad catchment of Khorasn Razavi Province was selected for determining the optimal level of land use and the effect of correct methods of management on maximizing net income of residents and minimizing the effect of soil erosion. Multi-objective linear programming model and simplex method were used in three different scenarios of 1) current land use conditions with current land management, 2) current land use conditions with improved land management, and 3) Standardized land use condition. The amount of net income and soil erosion were computed in rangelands, orchards, wooded ranglands, dry-lands and irrigated lands in all three scenarios and then the area of each land use was optimized, using optimization software. Results showed that land use optimization in Sheshtamad Watershed, decreases soil erosion, and increases total net income, although the amount is small, because of the conditions studied. The amount of annual soil erosion was reduced by 0. 08%, 0. 36%, 0. 75% and the amount of annual net income was increased by 3. 12, 20. 88 and 313. 75 thousand Rials, respectively, in the above three different scenarios, . The results also showed that in the case of some propoer management practices, the soil erosion reduces by 3. 25 times and net income increses by 6. 7 times.

Rainfall runoff models are used mostly in simulation of flood events. Also, calibration of rainfall runoff model parameters is an important and challenging issue in flood simulation. Due to random characteristic of these parameters, the deterministic optimization is not a suitable approach for calibration of rainfall runoff model. So, in this study, the SUFI (Sequential Uncertainty Fitting) algorithm is used as a stochastic approach and the optimized range of parameters were extracted. The obtain results shown, in calibration step, the correlation coefficient between observed hydrographs (three events) and the best generated hydrographs were more than 0. 9 and also, the average difference between observed hydrographs and the best generated hydrographs were less than 5 percent. Furthermore, in validation step, the correlation coefficient between observed hydrograph and the best generated hydrograph was 0. 99 and also, the average difference between observed hydrograph and the best generated hydrograph was 11 percent. So, the SUFI algorithm is a suitable approach in stochastic calibration of HEC-1 model.

Planning and management of water resources in watersheds require data, including, base flow and its index. These parameters are influenced by morphometric, geologic and hydro climatologic factors and have always been of the most important issues in hydrology. In this research, base flow and related index were extracted from daily stream flow data using two parameters recursive digital filters in 43 hydrometric stations of Kerman Province. Physiographic, climatic and hydrological parameters were calculated in GIS environment. Using factor analysis of 14 parameters, six factors were chosen as the most important independent factors. Then the regional equations were determined, using linear regression at 1% significant level. To compare and evaluate the accuracy and efficiency of the models, independence errors, colinerity and normal distribution of error were tested. Among the factors investigated, multivariate regressions were identified as the best estimator of base flow index in the study area.

In order to determine the role of hydrological statistic data periods on flood forecasting in Sefidrood Watershed, maximum daily flows were collected from hydrometric stations, thus seventeen valid stations with long-term statistical data period was chosen and in some cases which data were corrupted, data has been reproduced by considering common time base. . At the second step, maximum daily flow data have been divided in to statistic series with 10, 15, 20, 25, 30 and more than 30 years data periods. Fitting statistic distribution of Normal, Normal log, Normal log 2 parameters, Normal log 3 parameters, Pearson log 2, Pearson log 3 and Gamble were determined by “ Smada” software, also flood with two, three, five, 10, 25, 50, 100 and 200 return periods were calculated either. Statistic distribution for all of seventeen hydrometric stations were determined separately with RMSE method in Excel and SPSS for maximum daily flow. . Regarding zero-error in forecasted floods for long statistic data period (more than 30 years) in related return periods, compared with short statistic data period (10, 15, 20, 25 and 30 years), flood’ s estimated error was calculated for all stations. In general, results indicated that increasing of statistic period, will enhance the accuracy of forecasting in hydrometric stations, and applying short-term data period will result in high levels of error.