نشریه پژوهش های آبخیزداری
پیاپی 123 (تابستان 1398)

Shortage of water resources and the growing concern about the sustainable development have made the water supply for all of the potential needs nearly impossible.As an accurate prediction of river discharge is very important in water resources management, the development of a model to predict discharge has been carried out using the genetic programming and auto regression moving average on the Amameh Watershed located in the Province of Tehran. The long-term rainfall, temperature, discharge, relative humidity, and evaporation data have been used. Satisfactorily, the results showed that genetic programming had a lower error and could estimate the observed discharge. Furthermore, the number 54 model with inputs of temperature, rain, the delay in rainfall of up to two days, relative humidity, evaporation, and the delay in discharge of up to two days were considered as the best fit model with the errors of 0.001, 0.031 and 0.009 in the training stage and 0.002 , 0.032, and 0.009 at the testing stage respectively. On the other hand, the linear auto regression moving average models showed a much higher error; they could neither predict the high discharge, nor low flow and have not been able to provide satisfactory results. Therefore, the application of a genetic programming model is recommended due toits high precision with the main operators and the standardized data.

Construction of underground dams (UGDs) is a method of water harvesting in arid and semi-arid regions facing the drought crisis. UGDs are structures constructed in the hidden waterways that can store water in their upstreams. The most important problem in the construction of such dams is finding the right place. The purpose of this research is to locate and prioritize suitable areas for UGDs using the TOPSIS multi-criteria decision making method on the Sadeghabad Watershed, the Province of Fars. By performing field surveys and considering: slope percent, distance from fault, land use, and lithological units inappropriate areas were removed and a map of potential areas for the construction of an underground dam was prepared. According to expert judgement and review of scientific resources, 9 criteria, namely water quantity, dam length and height, reservoir storage coefficient, reservoir volume, abutment, slope, water demands (domestic, agriculture, and industry) and accessibility (road, village, and borrow area) were used to prioritize appropriate locations. Accordingly, 17 initial sites were selected based on expert judgment considering the criteria and overlapping of the base maps. The results indicated that water quantity and water demands with the weights of 0.308 and 0.2048 had the highest rating in priority in locating the underground dam, respectively. In contrast, the length of the axis of the dam and the supporting base of the dam with the weights of 0.019 and 0.023 had the lowest rating in priority. Finally, sites 15, 2, and 14 were given the first to the third priorities. Therefore, due to the serious limitations of groundwater resources in most parts of our country, and particularlyin the Province of Fars, these methods are useful for identification of suitable sites and construction of the UGDs.

The analysis of climatic changes in the future and its impacts on groundwater resources is very important. This phenomenon, in areas where the vulnerability of the water sector is significant in the current situation, can cause considerable damages and provide a desertification setting in these areas. The trend of water table changes in Sahraye Bagh Plain,Larestan investigated by using the data from 17 observation wells during the 2006–2016 period. Using the non-parametric Mann-Kendall test indicated the prosence of a trend at the significance level of 99%. Derivation of the trend line slope using the Sen estimator showed that the groundwater level of the plain was receding 10.2 m during the period, on the average. As the agricultural sector is the main consumer of the groundwater resources in the plain, the water balancesituation was predicted using the Effective Rainfall (ER) method to assess the climate change impact on observation water table changes. The  ER index changes were evaluated by the outputs of the HadCM3 model. The results showed that the ER index in the A1B, A2 and B1 diffusion scenarios will increase by 73.2, 76.8 and 36.8%, respectively. This situation will further the current shortage of water in the Sahraye Bagh Plain and aggravateduring the 2080-2099 period. The increasing trend of groundwater extraction will enhance the drop in the groundwater level if the current withdrawal continues unchanged.

Assessment of quantitative variationsof the surface water resources in the temporaland spatial scale in some watersheds the province of Ardabil will provide the possibility of balancing and optimal allocationof water resources in the current and future situations. Water resource managers need to have access to reliable information about the amount of available water and costs to decide on the allocation of this resource. The purpose of this study is to evaluate the temporal and spatial variations of excess volume in surface waters in some watersheds the provinceof Ardabil. The data collected at 23 hydrometry stations during the 1989–2014 periodin 21 watersheds were evaluated. The Water Stress Indicators (WSI and WSIef) were calculated. Excluding the Mashiran, Buran, Dostbeiglou and Samian stations, the remaining stations do not have too much excess water in most of the months and seasons, especially during the warm months. The difference between the results of the WSI and WSIef indexes indicate that in order to meet the needs of different sectors of agriculture, drinking and industry the province of Ardebil, not only the discharge of the rivers are consumed, but also the environmental flow is taken from the rivers. By exploiting the environmental flow,thus not considering it in thewater resources management system, the survival of surface-dependent ecosystems is at stake.

As the most valuable natural resources, protection and management of groundwater is vital. One of the best ways to protect groundwater resources is monitoring groundwater quality spatial variationsand then managing the water resources exploitations and the land uses. In this research, the spatial distribution of groundwater quality variables and the optimize water well network with acceptable precious in Shahrkord Aquifer is evaluated. According to the cross validation and the values of error evaluation criteria, the universal kriging model with linear trend, the ordinary kriging model with exponential semiovariogram, the Log ordinary kriging model with exponensionalsemiovariogram, the universal kriging model with linear trend with exponential semiovariogram, the log ordinary kriging model with panta spherical semiovariogram and the ordinary kriging model with exponential semiovariogram, has been selected for EC, Ca2+, Cl- and Mg2+, HCO3-, SO42- and Na+ and NO3- respectively. The quality-zoning maps of the Shahrkord Aquifer have been prepared. The results from the zoning quality map indicate that the groundwater quality reduced in central parts of the aquifer. In addition, in this research, to obtain an optimum monitoring well network was applied omittingmethod. Out of 35 observation wells, identified and removed six wells from the network. Using adding well method identified 11 wells as optimal points and added to the network.

Identification of the erosion-pron parts of a watershed is of at most importance if the soil conservation activities are to be implemented on it to mitigate sedimentation into the flood-receiving reservoir. Sediment fingerprinting is one of the most common methods used for quantifying source contributions of the suspended load. As the mixing models with different structures of sediment fingerprinting method are implemented, their advantagesand disadvantages should be identified. The applicability of eight mixing models,namely: Collins, Hughes, Motha, Slattery, Landwher, Modified Landwher, and Bayesian with the CLR transformation and the Dirichlet distribution were investigated in order to quantify source contributions of sediment deposited in the Lavar Reservoir, the Province of Hormozgan. Twenty-three soil samples were collected from the contributing watersheds, 9 sediments samples were extracted from the reservoir, and concentration of 56 elements were measured in each of the samples. The optimum composite fingerprints were identified by statistical methods and the mixing models were executed. Based on the results, four geochemical properties,namely Mn, La, Nd and Th were selected as optimum fingerprints. The results obtained by all of the mixing models were similar when the values of tracer concentrations in the sediment samples fall inside of those ranges in the source samples. When the values of tracers in the sediment samples fall outside of those values in the source samples, the mixing models with the same objective functions presented similar results. The results of Collins̛, model were similar to those of Hughes, and the results of Bayesian models were similar to those of Hughes the with the CLR transformation;the results calculated by the Motha were similar to those presented by Slattery, and results of Landwher were similar to the modified Landwher. Generally, applicability of the various mixing models in fingerprinting are different, as their outputs are dependent on the target functions, which are minimized in optimization.

Assessing performance of watershed management activities will provide valuable information to managers and decisionmakers for long-term planning. Stability of 70 masonry check dams was evaluated that have been constructed on the Kelestan Watershed, Shiraz, in 2006. Relevant information of these structures, namely position, number, type competence of materials, current performance, degradation status (intensity and location), type and culprits of damage were recorded during field visits, and the distribution map of the structures was prepared. Stabilitiesagainst subsidence, overturning and sliding were also investigated. The designed discharge of the check dams was to be correlated with the different return periods during the elapsed time. The results showed that as the designed discharge of the check dams for a 25-years return period had not occurred yet up to the evaluation date (2014), their stability cannot be evaluated based on the lower discharges. As to subsidence, no measurable settlement was discovered. Furthermore, 98.6 percent of the check dams showed stability against overturning and sliding and only1 (1.4 percent) of the check dams was collapsed completely. Signs of damage are observed in the check dams despite showing stability against subsidence, overturning and sliding. Poor quality building materials, unsuitable placement and piping are the main causes of damage on this watershed. To prevent the piping phenomenon, the soil under the structure must be removed and compacted in different layers.