IRANIAN JOURNAL OF WATERSHED MANAGEMENT SCIENCE AND ENGINEERING
Year:2018 | Volume:12 | Issue:42 |Papers Count:14

In the present study, performance of 6 Atmospheric general circulation models as: CGCM3, HADCM3, CSIROMK3 (collection of AR4 models) and CGCM1, GFDL30, NCARPCM (from the collection of model ATR) for simulation of climatic parameters include average temperature and precipitation using artificial neural network (ANN) in Caesar basin were evaluated. For training of artificial neural network model, perceptron forward method was used. According to performance evaluation of these models using maximum absolute error, mean absolute error, root-mean-square error and Russell Square Quality Representatives of the model, among AR4 and ATR models, AR4 models had better performance than ATR models and less uncertainty in simulating of climatic parameters (rainfall and average temperatures) in Caesar basin at 1996-2000. Between these 6 models, CGCM3 is the best performance in the simulation of climatic parameters for Caesar basin. CGCM3 and HADCM3 models have the lowest differences with observed climate parameters. Also, the results showed that CSIROMK 3. 0 and CGCM1 models have the most differences with observed climate parameters.

Bed material size frequency distribution of rivers is one of the key points to identify river characteristics. River bed armoring development is one of the controlling factors in sediment transporting and eroding processes of gravel bed rivers. In this research, field study was initially carried out on several gravel bed rivers in Khuzestan and Chaharmahal provinces. 24 hydrometeorological stations in 17 river reaches were sampled to characterize bed material gradation curve. With regards to bed structure of gravel bed rivers, samplings were made by surface and volumetric methods. Thereafter, sediment samples were differentiated in three categories of surface, armor and sub-armor layers. The collected field data were originally applied to derive regime relationships by using multivariate regression analysis. The effect of bed structure was directly studied in these relationships for the better understanding of that in the regime relationships.

The weather forecast data for future planning is very important in the fields of natural and human environment including the prediction of droughts and floods and so on. With the systematic planning, probable damages will reduce. In this study, the effects of climate change on drought conditions of North Branch of Zab River catchment located in the South West of Western Azerbaijan province, as the most important river plains of Piranshahr, during the period 2065-2046 using the indicators of drought (DI), SIAP and the Standardized Precipitation Index (SPI) has been carried out. Initially, daily data output of general circulation models of the atmosphere HADCM3 under the scenario A1B, A2 and B1, by statistical model LARS-WG Version 5, down scaled and the ability of LARS-WG in the simulation of past climate (2010-1992) studied for the mentioned station. So, using the precipitation data of drought situation to help mentioned indicators is discussed in annual terms, that the results conform these indicators proves to identify periods of drought. Considering to periods of drought that occurred in the observation data and results for the period is anticipated, there will be an increase in the severity and duration of drought in the study area in the coming years in Piranshahr station.

One of the problems of water resources systems in many countries is management and planning of optimal allocation of these resources. To date, several tools have been developed to model these systems according to the characteristics of the studied watershed. In this paper, by using WEAP model, water resources and downstream demands of Molla-Sadra, Doroudzan and Sivand dams, located in Maharlou-Bakhtegan watershed, Fars province, are simulated. On this basis, some management strategies were proposed under four management scenarios to combat the water shortages in demand areas, giving supply priority to domestic, environmental and agricultural demands. Simulations showed that the fourth scenario presents better results than other scenarios. So that with implementation of this scenario, water supply to the agricultural lands of Kamfirooz Plain, Arsanjan and Qasroddasht townships, Ramjerd agricultural lands and also water supply to Shiraz city could be provided with 100% reliability and drinking water of Arsanjan and Saadatshahr cities could be supplied with reliability of 39. 24 to 100%. Also, this model showed that water demand for agricultural lands in Kerbal Plain is 100% reliable in November and February, and in the rest of the months, the reliability for water supply is zero. Therefore, the agricultural lands in Kerbal Plain will face high water scarcity in March-June. Therefore, development of agricultural lands in Kerbal Plain should be reconsidered according to the simulation results.

The main factors in flood damages are the natural drainage pattern changing in urban and suburban areas. The main goal of this research is assessing flood risk; peak flow estimation and efficiency of surface runoff channels in Bandar-Abbas urban watershed and sub basins. For this aim, the digitization of data has been implemented using the GIS which includes drainage density, length of stream, land use type, geology, area and slope. Flood risk ranking was performed by the PROMETEEII model and the peak flow estimated with the Krigger method. Results and outputs show that, according to estimation of peak flow and past experiences, the surface runoff channels, are not able to convey flood more than ten-year return period and if a severe flood occurs, the city suffers a damaging flood. The Result of PROMETEEII shows that, Shilat and Sooro subbasins are the highest and lowest risk flood, respectively. Also, the most important criteria in flood risk are the length of stream and drainage density. Therefore, efficient mitigation measures are needed to reduce the flooding in urban watershed and improvement of channel system.

Soil erosion and watersheds sediment yield, due to improper management and overrated exploitation of natural resources, is greater than allowable amounts in Kermanshah Province. To mitigate these problems, watershed management operations, in vast area and volume, are implemented. This study was conducted to evaluate the effects of biological and mechanical watershed management operations on erosion and sediment yield controlling of Hajiabad-e-kangavar watershed. Watershed management operations included Gabions and check dams, storage channels, and cultivation of almond and grapevine. Assessment of variation of range condition and vegetation diagnosis accompanied by variation of soil erosion and sediment yield using MPSIAC and sediment volumetric was carried out. The results showed that planting operation in h-int sub-watershed and seeding almond and grape in h5-1 unit, while improving vegetation biomass production in about 100 kg/ha, it also reduced erosion and sediment yield about 15 and 8 %, respectively. Also, in h2 unit, that the dominant erosion aspect was bank erosion, gabion and check dam reduced soil erosion and sediment yields about 13%. Additionally, reducing about 5% of soil erosion and sediment yield in h8 unit contributed to execute biological operation of planting in this unit. Finally, biological and mechanical watershed management operations, in the entire sub-watersheds, were able to reduce erosion at the rate of one percent, over a period of 3 years after implementation. Main causes that lowered the efficiency of watershed management operation were the lower potential of erosion rate and sediment yield of this watershed.

Due to the increasing world population, exploitation and sustainable management of soil and water resources, it is essential to consider these resources to meet the needs. Therefore, Soil erosion and its control measures are the main prerequisites for soil and water resources management. It should also be noted that acid rain is also one of the factors that can cause soil erosion and destructive effects on the soil and the environment. In this study, the effect of acid rain on soil splash was investigated under laboratory conditions using rainfall simulator. For the acid rain test, different pH concentrations of 3. 75, 4. 25 and 5. 25 with the intensity of 40 mm/h, was used on the dry and saturated soil in splash cups. Paired t-test, Oneway and Two-way ANOVA (α =0. 05) were conducted using SPSS 23 and EXCEL 2013 software. Results showed that splash rates of acid rain with acidity of 3. 75 compared with the rate of non-acidic rain is a significant difference in 95 percent of the dry soil surface, but the acidity of 4. 25 and 5. 25 did not show significant differences. Also, comparison splash rates of acid and non-acidic rain, on soil saturation did not show any significant differences in any treatments despite numerical increase. The results of comparison of dry soil treatments with saturated soil treatments, show significant difference at 99% probability level, which indicates the direct effect of soil moisture on amount splash. The investigating interaction of soil moisture in dry and saturated conditions with different pH concentration of the rain, did not show any significant difference between treatments.

Groundwater and surface water resources are severely affected by the lack of rainfall. Several indices provided for evaluation of drought based on meteorological and hydrological variables. In this study, condition of meteorological and hydrological drought was evaluated by SPI, SPEI, SDI and GRI. The correlation of indices was evaluated at different time scales. Base on the results, SPEI has higher correlation than SPI with SDI at 9 and 12 months’ time scales and in the same month and one month later. Also SPEI has highest correlation with GRI at 24 and 48 months’ time scale that shows the impact of meteorological drought on groundwater level after two years and more. Knowledge of interval time between of meteorological drought as the main factor of drought would help to manager and planner for management practices in order to cope with drought due to lack of surface and ground water resources.

Fluctuation in precipitation is one of the most interesting issues in climate change. Precipitation has an important role in sustainable agriculture and water management. Trend series analysis is one of the methods used to detect changes in climate parameters. The aim of the recent study is to evaluate different methods including Mann Kendal, rating Mann Kendal and Sen’ s estimator slope tests to detect the trend variability of precipitation in monthly, seasonal and annual time scales in Kermanshah Province located in the west of Iran. In addition, TFPW (Trend-Free Pre-Whitening) method was used to remove autocorrelation on time series data. Trend analysis of precipitation carried out using 16 synoptic and rain gauge weather stations with 32 years data i. e., 1992-2013. The results showed that, precipitation trend analysis using Mann Kendal and rating Mann Kendal tests had the same findings in monthly, and annual scales. The results revealed that Mann Kendal TFPW was the best method to detect trend variability of precipitation in the region. Annual precipitation had a negative trend in 50 percent of weather stations which was significant at 5 percent level. The results also indicated that most of the weather stations had negative trend in annual and seasonal time scales. Winter and spring seasons showed the greatest changes which was significant at 5 percent level of significance. Although, the summer season indicated a positive trend in the whole synoptic stations. In addition, a significantly negative trend discovered in the months of Mehr, Azar and Esfand at 5 percent level. It could be concluded that land use changes associated with migration from rural areas to the urban ones were responsible for precipitation trend variability.

The first step form soil erosion is the soil splash that this step creates by the raindrops effect on soil surface. The raindrops can separate the soil particles and they cause the change of soil structure and increase soil erosion. Therefore, the study of effectiveness factors on splash erosion are including rainfall erosivity and soil erodibility can be effective in control of splash erosion. Two variables of rainfall duration and initial soil moisture can have more effect on amounts of splash erosion that have been perceived. The present study aims to the effect of rainfall durations with rates of 5, 10, 15, 20, 25 and 30 min and initial soil moistures with rates of 20 and 40 percent studied on splash erosion in rainfall intensity of 30 mm h-1 and scale of splash cup. The results showed that the variables of rainfall duration and initial soil moisture had significant on the rates of total and net splash in time unit and level of 99 percent. Whereas, the interaction effect of initial soil moisture and rainfall duration had not significant on total and net splash in time unit. The results also showed that, there was the inverse and significant correlation between rainfall duration and total and net splash in time unit, because the total and net splash in unit time decreased with increasing rainfall duration in both moistures of 20 and 40 percent. The results showed that the effect of initial soil moisture of 40 percent had more on total and net splash in time unit toward initial soil moisture of 20 percent.

Over the last decades, ground waters are considered as substantial water resources in many parts of the world. Unfortunately, the intensive use of groundwater resources has often affected ground water levels. Yazd-Ardakan region is one of the critical areas from water resources perspective. This paper analyzes the impacts of climate change and human pressures on Yazd-Ardakan aquifer. HADCM3 circulation Model and different scenarios were used for future climate changes prediction in the study area. Water levels in the study aquifer were simulated using Artificial Neural Networks and HARTT model for present and future (2016-2033) periods. Validation of applied models showed that HARTT model has good ability in modeling the water table fluctuations. Ground water fluctuation prediction by HARTT model showed that if climate changes and groundwater extra exploitation continues, this trend will lead to nine meters degradation in aquifer level till 2033 year. The continuation of this situation will involve serious degradation of aquifers in quantitative and qualitative terms. Therefore, with regard to limited water resources and fragile climate of the study area, it is suggested that decision makers consider this issue in planning the future perspectives of the study area.

Groundwater exploitation is exceeding the safe aquifer yield as one of major source of fresh water. Unconfined aquifer of Damaghan Plain located in vicinity of central desert of Iran encountering rapid water table decline due to over exploitation. This research focuses on quantity of aquifer loss to prevent any further the water table decline. This research carried out by use of Fuzzy method in three different models and nine subsequent sub-models. Three models distinguished based on water table variations in three levels of low loss (0-0. 7 m), medium loss (0. 7-3. 5 m) and high loss (3. 5-7 m). In all three models, recharge quantity and water table loss are inputs and aquifer deficit as an output to the model. In each of three sub-models of each model; 11 MCM as a natural recharge, 21 and 31million cubic meters as aquifer loss, respectively. By changing of water table, it is possible to get different outputs as the discharges. This operation has been carried out twelve times for each sub-model, so twelve points have been obtained as the various discharges. Then, these points are distributed by the power of two and three fitness functions. Ultimately, the appropriate recharge to compensate the aquifer deficit is defined as 21 MCM.

Heavy rainfall is one of the most important climatic events, and if the proper planning is not done, the environmental and economic damages will be lost without access. In the present study, future changes in heavy rainfall of the southern Coasts of the Caspian Sea were predicted with regard to global climate change in the period 2011-2030. For this purpose, changes in the rainfall pattern of 10, 20 and 25 millimeters and more were studied based on the data of seven synoptic stations (Anzali, Astara, Babolsar, Gorgan, Noshahr, Ramsar and Rasht). The daily rainfall data in the period of 1961-2010 after verifying their accuracy, were simulated using the LARS-WG model. After controlling the compliance of the simulated values with the current data, daily precipitation was expected in the upcoming period (2011-2030). Three indicators of heavy rainfall of 10, 20 mm were calculated by the R-Climdex model for the observation period and the upcoming period, and the results showed that during the period in the future, in all stations in the area, the number of days with a 10mm heavy rainfall will be reduced. The comparison of the average number of days with a very heavy rainfall of 25 mm and more indicates that in the following period, in all stations in the area, the number of days with a very heavy rainfall of 25 mm and more will be added. Also, the results of the comparison and analysis of the number of days with a very heavy rainfall of 20 mm in the base period and the upcoming period indicated that; in all stations in the region in the upcoming period, the number of days with heavy rainfall of 20 mm will be added. In total, in all stations studied, Anzali station will experience the largest number of days with heavy rainfall of 10 mm and a very heavy rainfall of 20 and 25 millimeters.