نشریه پژوهش های آبخیزداری
پیاپی 125 (زمستان 1398)

Natural resources of Iran is critically facing various threats including climate change, droughts, pollution (water, soil and air) and land degradation induced by inappropriate land management, i.e. unsustainable development practices, particularly on sloping tracts in mountainous areas. The Hable-Roud Basin conditions are the same as those of the entire country without exception. Therefore, to overcome these maleficient activities, development of various management options seems inevitable. After drawing up a preliminary list of proposed management options for the Goursefid Sub-watershed of the Hable-Roud (river) Basin through participation of local communities and experts’ input, selection and prioritization of the options were modeled using the participatory approach and application of the multi-criteria decision making methods within the mDSS software. Ultimately, suitable locations for an implementation of the selected options were identified and positioned across the study area with the participation of representatives of the local communities and experts. The results indicated that the main category of “land management and planning” options were preferred using all of the group decision making methods. Moreover, “development of an integrated watershed/water resources management plan”, “development of landuse plan at different scales” and “identification and training of new job opportunities and alternative livelihoods” were ranked first to third, respectively. Therefore, more attention should be paid to land management and planning options to better administer the watershed.

Given that, a lot of soil lost from watershed area by erosion factors. The application of management methods is necessary for soil loss control. Therefore, the use of the available, economical and environmentally friendly conditioners can be the suitable approach in soil loss and runoff control. On the other hand, the soil and water conservation need to the suitable amount determination of soil conditioners to be in addition to reducing costs, from water contaminants prevented with application of chemical fertilizers. However, the optimum amount determination of soil various conditioners with quantifying aim of this effect less attended on runoff and soil loss components. Accordingly, in this study, the effect of various amounts of manure compost with rates of 2.25, 4.5, 9.0 and 18.0 t ha-1 on amount of runoff and soil loss from experimental plot with area of 0.5 m2, slope of 20 percent, was conducted using rainfall intensity of 50 mm h-1 for duration of 10 min in agricultural soil that it collected from Sari province in year 2018. The results of statistical analysis indicated on the significant effect of various amounts of manure compost on changes of increasing time to runoff and decreasing runoff volume and coefficient, soil loss and sediment concentration in level of 99 percent. Also, the study of conservation effect and grouping various amount of manure compost showed that the compost with rate of 9.0 t ha-1 for the same effect with amount of 18.0 t ha-1 on changing runoff coefficient and sediment concentration can suggest as the optimum and practical amount in natural conditions.

Groundwater resources have shrunk noticeably in arid and semi-arid areas in recent decades. Therefore, determination of the most important problems of the aquifers and the best management strategies is important. The purpose of this study is to identify in the causes of the imbalance of groundwater in the Abarkuh Plain aquifer, in the Yazd Province. To attain this, the criteria and sub-criteria of groundwater problems were determined using Analytical Hierarchy Process (AHP) method in the Expert Choice software. Then, aquifer management strategies were designed using the same process (AHP method). The results indicated that agriculture, with a relative weight of 76.00% compared to industry and domestic water is the most effective consuming sectors in creating the aquifer imbalance. The most important agents in this sector were over-exploitation of the aquifer (22.50%), competition in agricultural water utilization (20.10%), irrigation systems (14.50%), cultivation patterns (12.50%), cultivated land area (8.20%), illegal irrigation wells (6.00%), and the development of high water demand industries (4.50%). Furthermore, the most important solutions for crisis management were irrigation system reform and cultivation pattern correction. To acheive these solutions, management strategies including equipping the wells with the volumetric counters, prevention of illegal pumping, separation of drinking from sanitation water, and development of the low water-consuming industries are suggested.

Over-exploitation of a limited resource, especially in arid and semi-arid regions such as Iran, entails a strict management of groundwater. In this context, identification of changes and fluctuations in groundwater level can help to make the right decision. The Gravity Recovery and Climate Experiment (GRACE), a joint mission of NASA and the German Aerospace Center, makes detailed measurements of the Earth's gravity field anomalies and fluctuations in groundwater resources at a spatial resolution of a few hundred kilometers. Due to the lack of the in-situ measurements at a regional scale for the quantitative groundwater monitoring, this satellite's unique data are used to monitor the quantitative annual changes in the groundwater resources. Data processing was performed on the Google Earth Engine Web platform using the JPL, GFZ and CSR algorithms. Results were compared using the piezometric data from 2008 to 2018. This comparison was performed by a linear regression between the changes obtained from the GRACE algorithms and the piezometric data, which resulted in a 69% correlation of these two methods. In order to perform spatial and temporal analysis of the water level of the aquifer, the zoning was performed using the ArcGIS software. The results indicated that, the water level in the studied aquifer has been significantly reduced during the 2008 to 2018 period due to a lack of rainfall, thus the net recharge and over-extracting.

The present study is aimed at estimating the suspended load discharged from watersheds in the Province of Hormozgan. The mean annual suspended loads were considered as the dependent variable and 21 parameters of morphological and climatic factors were selected as the independent parameters. The data were collected from 19 hydrometry stations for a 21-years period (1991–2011). This analysis is presented in two steps; a principal component analysis (PCA) was further applied to extract the underlying factors (principal component) and use the hierarchical clustering analysis in order to identify homogeneous groups. Multi regression was performed to identify the contribution of each variable. Different clustering scenarios were considered for selecting the optimal number of homogeneity groups, and their overall impacts on cluster validation indices were assessed. These three scenarios include dependent variable, independent parameters and the combined variables. The performance of the models was evaluated using the coefficient of determination (R2) and the Nash-Sutcliffe model efficiency. The watersheds were divided into two clusters and multiple regression models were derived for each homogenous region. Eventually, the models with coefficients of determination of 0.78 and 0.84 were used to estimate the mean annual suspended load. It is recommended to study more watersheds with different condition to reach the plurality and improve the quality of these models for estimation of the suspended load in the ungauged watersheds.

Land degradation in different climates drastically disturbs natural ecosystems and reduces the biological production potential of the resources. To investigate the role of geological criteria on land degradation in rangelands surrounding Eshtehard, the map of units was prepared by overlaying and crossing maps of slope classes, land uses, and geological formations using the ArcGIS 10.3 software. Three indices of erodibility, salinity and permeability for each unit were considered and classified. The weights of criteria and consistency ratios were calculated by the AHP method. The TOPSIS method was used to prioritize the alternatives. The weighted normalized values, Euclidean distances, and the relative closeness to the ideal solution were calculated and top priority was given to the land degradation potential (DP) of the units. The results indicated that the relative closeness to the ideal solution obtained from the AHP-TOPSIS technique ranged from 0.002 to 0.991. Accordingly, the study area contains four categories of potential or severity of land degradation, namely: 20872.709 ha (37.97%) of the area with low DP, 1470.297 ha (2.67%) of the area with moderate DP, 1844.861 ha (3.36%) of the area with high DP, and 30788.02 ha (56.00%) of the area with high DP.

Wetlands are an integral part of the semi-arid and arid ecosystems, which are inundated during major floodings and are transformed into sources of particulate matter during drought. This phase of their life cycle is very disturbing as they affect breathing in downwind areas and result in many pulmonary diseases. Thus their management is very challenging. As the Mansuriyeh Wetland (MW) is transformed into a dust source when dry, and threatens the City of Ahvaz with dust storms in the lean years, and this is mainly caused by an eradication of the vegetative corer, it was decided to survey the area when the MW was brimmed with floodwater. This was achieved benefiting from the images collected by the Landsat TM, ETM+ and DLI during the June of 1988 through the same month in 2017, and the rainfall data provided by the National Meteorological Organization. Analysis of the information was carried out in three steps: preprocessing, preprocessing and post preprocessing using the support vector machine (SVM) along with the ENVIs software. Likewise the image were classificed into the inundated areas the land covered with vegetation, water and the bare land. Truthfulness of the image was validated through Google Earth employing the total accuracy and the kappa procedures. The percentage of the area covered by each class was determined through the GIS zooning. The area contributing water to the MW was determined as its watershed, the rain-gauging network was plotted on the maps, and the mean annual precipitation of the entire watershed was calculated and drought occurrence and its intensity were determined using the standard precipitation index (SPI): the R2 for this item was 0.6. Therefore, variation of the MW as a dependent variable is related to the drought as an independent variable. Thus drought is 60% responsible for dust formation. Other variables, namely numerous small earth banks, oil well drilling installation and agricultural activities may also contribute to dust formation. Variations in the extent of the bare area and its relationship with the dust formation indicated that 80% of the MW had dried during the previous10 years. Moreover, up to 100% of the area had been entirely without a vegetative cover in some of those years. Salinity of a fine- grained soil, also made it a potential source of dust storms that invaded the Ahvaz Metropolis.