مجله مدیریت آب و آبیاری
سال سوم شماره 1 (بهار و تابستان 1392)

Hammerstein-Wiener (HW) models are capable in describing nonlinear dynamic systems. These models are nonlinear and have been widely used in a wide range of sciences due to their simplicity and having a physically-based concept. In this research، for the first time in hydrology and water resources management، three different structures of these models using daily temperature and precipitation data as model inputs were applied to simulate Taleghan Reservoir daily inflow using R2، RMSE، SRMSE، MAE، d and PEP statistics and criteria. To do this، the reservoir data from 2006 to 2011 were utilized. The results obtained with (HW1) and without (HW2) data pre-processing were compared with the results achieved from two different structures of artificial neural networks (ANNs) including (i) Feed-Forward ANN with two Hidden Layers (FeedF2) and (ii) Generalized Regression Neural Network (GRNN2). The results revealed that the HW models outperformed the ANN models. In particular، the mean and standard deviation of the inflow time series were simulated very accurately. The SRMSE values of the HW1 model were 33% and 37% and while these values for the HW2 model were 28% and 43% over calibration and validation phases، respectively. Meanwhile، the accuracy obtained over calibration and validation phases were 50% and 71% for FeedF2 and 58% and 50% for GRNN2، respectively.

The determination of temporal and spatial salinity in tidal rivers is significant in supplying water for agriculture purposes، particularly where there is no controller dam at the downstream. In this research، the COHERENS model was applied to study the hydraulics of water flow، salinity distribution and transmission at the Bahmanshir river. COHERENS is a 3D multi-purpose hydrodynamic model which is coupled to biological، resuspension and contaminant models. The model was calibrated and validated against water level and two wet and dry duration periods in 2002 and 2003، as well as salinity observation during a spring tide in 2003. Three sensitivity scenarios were conducted based on different river flows and wind conditions. The model results showed that salinity intruded further upstream under scenarios with low flow and downstream wind. However، the responses of salinity stratification to different environmental forcing function were not different in various portions of the river. Finally، using time series of salinity frontal movement، spatial and temporal patterns of salinity intrusion، and the best spatial and temporal thresholds for water withdrawal along the river were assessed. The results also indicated that adopting optimal compound conditions of discharge and intermittent water harvesting could be considered as an effective and practical way to achieve qualified water for agricultural activities.

In the last decade، the water level of Urmia Lake has experienced a dramatically drop. Although the causes of this lose have been investigated، the significance of groundwater supplies had not been concerned so much. In the present research، groundwater resources around the Lake were explored as its water supplier. The number of wells and groundwater withdrawal has been increased because of cultivation، dry farming، and agricultural activities growth; so aquifers of this area have been affected by saltwater influx. In this research، water surface contours used for evaluation of the Lake’s groundwater inflows fluctuation and changes of aquifers’ salinity were assessed for (the Lake) water interactions in two periods (2001 and 2011). According to the results، in Mahabad، Tabriz، Azarshahr، Shabestar-Soofian and Ajabshir aquifers the groundwater flow direction has changed from lake to aquifer. This means that the groundwater boundary input from these aquifers to the Lake are cut down. Large parts of aquifers around the Lake have been subjected to saltwater influx by change of groundwater flow direction whereas electrical conductivity of Tabriz، Miandoab، Kahriz and Shiramin aquifers increased considerably. In conclusion، eastern aquifer situations are more critical than western ones and highly vulnerable to quality degradation.

The groundwater resources of the Urmia plain have been under intensive tension for the last recent years. This has caused the production and observation wells to become dry and in some local places well deepening to take place. In some other locations، the groundwater level is high and there is a danger of local water logging condition along with its associated drainage work. For the settlement of welfare groundwater resources، the modeling practice was used for the depiction of Urmia plain groundwater resources system reactions against different imposed management and executive scenarios. By the present work، the modeling with 28 observation wells took place for the year of 2008-2009. The comparison of calculated hydraulic head contour lines with that of the observed hydraulic head in nature showed a sound performance of the model. This made to impose and apply different scenarios in the model. To go forward، the decrement of 25 percent and the cease of pumping rate at western part of the plain caused average groundwater level rise of 0. 5 to 4 meters in eastern part of the plain. This led to have an average groundwater level fall of 1 to 3. 5 meters، respectively.

The multi-criteria decision making model is an important tool for decision making in water resource management. In this paper، the TOPSIS model was used to rank seven flood management options in the Gorganrood river flood management project، including conservation of natural condition، Golestan reservoir management، levee construction، diversions-channel construction، flood forecasting and warning system، flood insurance، and integration of flood warning system and flood insurance. Economical، technical، social and environmental qualitative values and criteria weights were determined by expert judgment and used to evaluate options. Due to limitations in the TOPSIS model، the M-TOPSIS model was used and obtained results were compared with the TOPSIS model outputs. The results showed that the M-TOPSIS model would produce better results for ranking options and sensitivity analysis of criteria weights. Therefore، given the significance of social and environmental criteria، this model is recommended for ranking flood management options.

One of the water resources modeling requirements is sufficient knowledge of long-term series of meteorological and hydrological parameters. In this study the nearest neighbor resampling method presented by Lall and Sharma was developed. In the developed model، the KNN regression was used for time series forecasting instead of local polynomial used in the developed algorithm by Prairie. In this case problems caused by polynomial degree estimation were solved. This caused that multivariate time series simulation became feasible. To evaluate the performance of the developed model recorded data in the Kawtar hydrometer station located on one of the main branch of Mahabad River and Mahabad synoptic station were used. The results from time series simulation showed that the developed model is able to keep important statistical characteristics of historic series. In addition، it could solve the classic nearest neighbor resampling method problem in order to produce values not seen in the historical record. Also، this model showed that it could simulate the multivariate hydrologic series.

Vegetation cover on a variety of different land uses in different parts of a city creates different forms of heat flow that this، in turn، generates the main framework of urban microclimate. The objective of this study is to survey the effect of land cover type on air temperature in the Isfahan city. To do this، five regions in the Isfahan city with different land cover type were selected. In each region automatic weather stations were installed in order to measure air temperature. The measurements were logged over a year every 5 min; then an hourly average of temperature data was calculated for all analysis. The results showed a significant difference between air temperatures in different parts of the city covered by different land cover type. The highest maximum air temperature difference was 3. 51° C between Station 2 and reference station in November. The highest minimum air temperature difference was 8. 15° C between Station 1 and reference station in July. The results also showed that in all seasons especially in spring and summer، there is a significant difference (P<0. 01) between air temperature in the city and air temperature in the reference station. Air temperature in the city was strongly influenced by the land cover type and extent of vegetation cover. Therefore، the measurement of air temperature in the city is necessary for irrigation management.

Due to the important role of subsurface drainage in managing the ground water level، there are many researches focused on finding a new and more economic way to develop subsurface drainage technologies. Lack of proper drainage system in northern Iran has caused huge implantation of rice and it is impossible to have second implantation in this region. One reason of insufficiency of current drainage systems in this region might be the absence of envelope material like sand and gravel or in some cases the long transportation of gravel envelope materials to the project site which rises drainage cost. In this region، rice husk is considered as wastage of rice production. Production of rice husk is estimated to be 600 thousands tons every year in Iran، which can be potentially used in drainage systems. The main objective of this research is to investigate the feasibility of using rice husk instead of drain pipe and envelope materials. The performance of drainage system using rice husk was studied in a laboratory model and the obtained results were compared with the conventional gravel envelope materials in terms of their drainage capacity and reaction factor for water table drawdown. The maximum drainage discharge was measured to be 0. 13 and 0. 12 lit/s in the case of rice husk and envelope materials، respectively. The corresponding values for the reaction factor were estimated to be 8/937 and 9/899 day-1، respectively. The results also showed good functions of rice husk in decreasing water table and supporting the drainage needs.

Soil salinization is a process in which the accumulation of soluble salts in soil profile can affect soil physical and chemical properties، such as osmotic pressure، permeability and hydraulic conductivity. These، in turn، can seriously impair or completely stop the growth of plants. In this study، four theoretical models for predicting soil leaching contains including Series of Reservoirs Model (SRM)، Theoretical Plate–Thickness Model (TPTM)، Convection – Dispersion Model (CDM) and Numerical Model (NM) were studied in order to select and introduce the best model for predicting ultimate soil salinization. The results of these models were compared with real data obtained from field experiments. To do this، 15 basin plots (each has one square meter) were firstly built. Then، five leaching depths of 20، 40، 60، 80 and 100 cm were applied to basins in three rows. Results revealed that the investigated models showed different performance for the different depths of leaching. Overall، Series of Reservoirs Model (SRM) was able to estimate the ultimate salinity more accurately.

Concerns about nitrate pollution in groundwater and downstream systems Cause development of surface water management system to reduce losses of agricultural drainage water nitrate in subsurface drainage Using subsurface irrigation from existing drainage lines، drainage water during the growing season and out of season is controlled. The overall objective of this study was to evaluate the effect of controlled drainage on nitrate losses via drainage outlet and a physical model used to simulate the conditions of a real farm. Plan includes of six treatments، one treatment free drainage (FD) output at a depth of 80 cm from the soil surface drainage and controlled drainage treatments (CD1، CD2)، which drains the water table controlled at 45 and 25 cm، respectively، at a depth of the soil surface. Each level has two drainage treatments applied nitrate fertilizer (urea) N1 (100 percent) and N2 (50 percent). The results showed that the amount of drain output، there are significant differences between the treatments drained (P< 0. 0001، F=45. 42). Controlled drainage treatments (CD1 and CD2) compared with treatment FD، 57. 9 and 80. 5 percent have reduced the volume of drainage water، Respectively، and CD2 treatment the amount of drainage water compared with CD1 treatment 53. 8 percent reduced. 100 percent of the nitrate fertilizer، controlled drainage (CD1 and CD2) in comparison with free drainage (FD) rates of nitrate loss to the 55. 8 and 82. 5 percent have reduced، And 50 percent of nitrate fertilizer، the amount of nitrate loss from controlled drainage to the 30. 3 and 70. 4 percent، respectively. Controlled drainage can be improved to reduce the role of nutrients in the soil and reduce nitrate removal.