مجله تحقیقات منابع آب ایران
سال هفتم شماره 2 (پیاپی 20، تابستان 1390)

Currently uneven distribution of limited water resources in addition to growing urban and irrigation water demands have severely increased water shortages in Iran. Inter-basin water transfer projects are among important infrastructures used by water managers and planners to supply for the needed water. However due to the complex technical, socioeconomical, and environmental aspects of these projects, in every stage of the decision making process, group multi-criteria should be considered. In this article four proposed routes of water transfers from the Aras River to the Northeastern part of the Urmia Lake in Iran are evaluated. The effective criteria including environmental impacts, cost of construction, simplicity of the construction, and the social acceptance are weighted by three stakeholders. Using the ordered weighted averaging and fuzzy quantifiers the group weights are obtained. Then using the four multi-criteria decision making methods (simple weighted averaging, TOPSIS, compromise programming, and ordered weighted averaging methods), the different alternatives are ranked and finally the best and the most robust water transfer route is selected. Results showed that the simple additive weighting and ordered weighted averaging methods are more useful methods for group multicriteria decision making on water resources development infrastructures.

In this study, optimal operation of multi-reservoir systems has been compared with the results of the related single-reservoir operation. In fact, in optimal simultaneous operation of reservoirs considering the effects of upstream reservoirs on downstream ones, the macro operation is preferred. A threereservoir system of KaroonV-Bazoft-KaroonIV dams is studied for different objectives of supplying downstream demands and generating hydropower. The Results have been obtained for three methods; nonlinear programming (NLP); standard operational policy (SOP) and rule curves, for a 48 month period. The rule curves which present release volume as a function of the reservoir storage volume and the river discharge, has been selected as the preferable operational policy for both objectives in the system. Validation of the suggested curves has been tested in a dry period.

Conjunctive use of surface and ground water resources is one of the aspects of integrated water resources management. In this paper, conjunctive use of water resources has been studied for arid regions in which the only source of surface water is the water transferred into the region. For this purpose, first, the region's groundwater has been simulated using the Modflow-Pmwin model. The results have then been used to develop an optimization model with a genetic algorithm and different alternatives have been investigated toward optimal use of water resources. Obtaining monthly patterns for water withdrawal based on controlling an aquifer's level is the main objective of the optimization model. Yazd's aquifer in central Iran has been selected as the case study. The results of the optimization model showed that supplying all the demands considering the present condition for the imported surface water (max 50 MCM annually), will cause a 2 meter fall in the aquifer's level in 5 years. An annual increase of 40 percent in the amount of imported surface water should be reached in order to meet all the demands with negligible drop in the aquifer's level.

Earth science methods for mapping, discretization, and separation of homogenous regions are recently used extensively to estimate the natural landscape response to hydrologic processes. For more homogenous study areas, the accuracy of the precision increases and the operation of water resources management system and/or natural wizard controls are less complicated. There are several methods to natural landscape discretization to identify homogenous regions. Because of continuity in landscape specifications, the use of Fuzzy classification/ clustering methods such as Fuzzy CMean (FCM) can be a desirable choice. In this study the FCM was used for discretization of homogenous regions in regards to runoff generation for Walnut Gulch Experimental Watershed (WGEW) located in southeast Arizona. This watershed is selected to benefit from the quality and adequacy of the hydrologic data. The process of choosing and preparation of data was addressed earlier in texts. The Principal Components Analysis (PCA) was performed and then the three essential steps for making decisions based on the FCM method was taken; determination of appropriate fuzzifier; controlling of Confusion Index (CI), and optimization of number of clusters using validation indices. It was shown that use of these validation indices would surely not lead to determination of optimal number of clusters and therefore a rational method was proposed.

Interaction of the saline water originated from the sea or the ocean with the riverine water is an important issue in estuarine systems. The intrusion of salt water in estuaries affects the quality of groundwater used for different purposes such as drinking, agricultural, and industrial consumptions. Several methods have been introduced by the investigators to control this natural phenomenon. The Venturi control method, submerged tidal barriers, and air curtains are examples of these methods. In this paper, the efficiency of the Venturi method for salinity intrusion control was studied for the Arvand estuary in south-western Iran. The performance of this method was assessed using three different discharges; the mean annual discharge (1050 m3/s), the minimum annual discharge (520 m3/s), and an assumed low discharge of 260 m3/s. A laterally averaged two-dimensional numerical model was used to simulate the salinity intrusion in Arvand estuary. The model was first calibrated using field data and then different scenarios were simulated. Results indicated the efficiency of the Venturi control method in decreasing the salinity intrusion length.

Probable maximum precipitation (PMP) is the maximum amount of rainfall which theoretically is supposed to fall on a specified point or region. In this paper two statistical methods of Hershfield (in two different approaches of standard and revised, as a point prediction) and multi-station (as a regional method) is compared for 33 raingage stations located in the Atrak watershed in north-eastern Iran. Extreme value type 1 and its two alternatives of transformed and cut-off distribution functions, which can handle a finite limit for rainfall as the return period increases without bound, was adopted for the multi-station approach. There were unrealistic results for the standard approach of the Hershfield method. Varions of dimensionless ratio of PMP for revised approach of Hershfield to the maximum amount of daily rainfall was in good harmony with other studies conducted in vast different climatological regions. The regional PMP by multi-station method were smaller than point PMPs for just 7 stations. This result may not be uncorrect, yet we proceeded for the first time in a reverse algorithm and calibrated the behaviour of the limited reduced variate parameter for the region. The resulting PMP was smaller than just one station. So it seems that the regional PMP may be equal to the maximum of the point PMPs of revised Hershfield method. This result is just drawn for only one region and should be confirmed by other researches.

Evaporation is one of the major components of the hydrologic cycle and its accurate estimation is of paramount importance for many studies such as hydrologic water balance and water resources planning and management. Evaporation is a complex and nonlinear phenomenon which depends on several interacting climatological factors. In this study, eight combinations of weather parameters were used as input data for estimating pan evaporation (Ep) for the northern part of Iran. Daily observed weather data for a ten year period (from 1996 to 2005) were used from 8 weather stations located in the southern coasts of the Caspian Sea. This study indicated that the minimum weather data required for estimation of the pan evaporation are maximum and minimum air temperature, relative humidity, wind speed, and sunshine hours. For the data that was studied, the Root Mean Square Error (RMSE) and the coefficient of determination (R2) for the comparison between observed and estimated Ep are 0.32 mm d-1 and 0.93, respectively. A graphical comparison between the observed and the predicted values of Ep showed that 76 percent of the values lie within a scatter of ±15%.