mohammad danesh yazdi

Determining the contribution of each of the effective processes to river flow plays an important role in how accurate these processes are estimated via hydrological modeling. Although water balance provides an overview of the volumetric changes of its components, the origin of the outflows and their temporal changes require utilization of approaches based on water tracking. In this study, we developed a three-dimensional physical and integrated hydrological model and coupled it to a water tracking model (ParFlow-CLM-EcoSLIM) to determine the contribution of rainfall, snowmelt, and groundwater to streamflow and evapotranspiration. Also, the distribution of the travel time of outfluxes has been simulated and studied. To demonstrate the applicability of the developed models, we chose the Godarchay basin, located in the southwest of Lake Urmia, as the study area. The results showed that snowmelt is the main source of river discharge and evapotranspiration in the region, such that the average contribution of snowmelt, rainfall and groundwater to the runoff production during a water year, is equal to 56%, 5% and 39%, respectively. Also, about 55% of the incoming snow during a water year is stored in the soil after the process of melting and infiltration, and is then removed from the system in the following years; while only 22% of new rain is stored in the system and 78% of it leaves the system in the same year.

Controlling water consumption in agricultural sector requires an appropriate understanding of the interplay between water resources, water consumption and agricultural economy. This study aimed to develop two hydrological and agro-economic models in the Mahabad study area (located in south of the Lake Urmia) in order to investigate the effects of climate change on the volume of water entering the Mahabad dam, explore long-term changes in gross irrigation needs, and study the impact of the crop pattern change on the gross irrigation need and the agricultural economy of the region. The results showed that if the agricultural water consumptions are controlled up to the year 1419 (Persian Calendar), the increase in the volume of water entering the Mahabad Dam under the climate change scenarios A1B and B1 can reduce the current withdrawal from surface and groundwater sources. It would also promote the possibility of release from the Mahabad Dam to partially provide the environmental flow of Lake Urmia. We further found that the net value of the crop production in the past years was much lower for wheat and barley compared to other crops, which explains the lack of economic justification for the cultivation of these two crops. The amount of production and the net value of sugar beet production showed a significant growing trend, which is in a clear contradiction to the policies of reducing agricultural water consumption by 40%. In case of increasing the cultivated area of water-rich crops in the region, the greatest stress on groundwater resources will be under the climate change scenario A2.

Accurate slope map and the governing river network of a river basin are key inputs of hydrologic models. The purpose of this study was to investigate the effectiveness of the PriorityFlow tool in topographic data processing with the aim of improving slope map extraction in the eastern Faryab Basin. PriorityFlow is a tool in the R programming environment, which aims to generate the correct slope map and to form a network of continuous pathways that matches the observed river network. To process the digital elevation model and prepare the slope map, three input files were used, including the digital elevation model, the representative map of the watershed and the representative map of the observed river network of the study area. After producing the slope map using this package, the obtained results were compared with the outputs obtained from other traditional tools available in the Parflow hydrological model. Specifically, the river network map related to the two slope maps were extracted by the Parflow model under the condition of very low permeability of the domain surface and compared with the observed river network of the study basin. The results showed that the slope map produced by the PriorityFlow tool has led to the production of a more accurate river network that matches the real river network of the eastern Faryab basin. Also, this software package is able to produce the slope map with enhanced accuracy and based on non-diagonal connections along the cell levels in the digital elevation model of the study area.

In this study, long-term changes in the precipitation pattern and how they affect the future flood events were explored by collecting, completing and validating precipitation data in the Karkheh, Dez, Karun, and Great Karun Basins. Also, the depth and frequency of precipitation in the water year 2018-2019 have been carefully investigated. Finally, the quality of precipitation forecast and awareness by some official organizations has been discussed. The study area has a sufficient number and density of reliable meteorological stations. However, this does not hold for the synoptic stations in mountainous areas, such that only 4% of the stations have recorded data in more than 10% of the entire 30-year statistical period. The results showed that the climatic trend of the region is on average in the direction of decreasing precipitation amount. The investigation of rainfall pattern has revealed the continuation of high soil moisture due to the increase of low rainfall events in recent years, which can lead to enhanced probability of flood occurrence. The analysis of April 2019 precipitations showed that in the entire study area, the amount of precipitation was 24% to 108% higher than the last 10-year average. The return period of total precipitation in Ahvaz station in the water year 2018-2019 was 297 years, which is unprecedented. In addition, the forecasts of the Iran Meteorological Organization and the Water Research Institute for the flood of April 2019 in the Khuzestan province were significantly erronous compared to the observations.

Human interventions, including land-use change and encroachment on river boundaries along with the impacts of the climate change have resulted in an increase in flood damages. This study aimed to identify and analyze the factors intensifying the floods of April 2019 in the Khuzestan province. To this end, we determined the return period of large floods in the region in April 2019; investigated land-use changes between 2000 and 2018 by using the random forest classifier; explored the changes in the soil moisture using remote sensing data; and analyzed the rule curve of the Karkheh and Dez dams. The results showed that the discharge observed at the Jelogir station, as the nearest station upstream of Karkheh Dam had a return period of 262 years, which is far greater than the return period of historical floods in the study area. The weak correlation between runoff intensity and antecedent soil moisture at 5% confidence level during 30, 45, 60 and 120 days before the flood indicated that beside the antecedent soil moisture other factors such as rainfall intensity and snowmelt were contributing to the intensified flood. We further concluded that the change in the land-use between 2000 and 2018 in the study area cannot be considered as a strong factor in the intensification of floods. Finally, the operation of Dez Dam in the water year of 2018-2019 had a much more effectiver impact on the flood control of April 2019 compared to the operation of Karkheh Dam.

Evapotranspiration is one of the key components of water balance in a basin. In recent decades, several methods and models have been developed for estimating evapotranspiration using remotely sensed data. In this context, utilizing the surface energy balance equation has led to the development of Surface Energy Balance (SEB) models, such as SEBAL and METRIC. Despite the extensive usage of these models, their application is still challenging due to the underlying algorithm complexity and the time consuming process of selecting cold and hot pixels by an experienced user. The goal of this study is to develop and introduce a new toolbox within the MATLAB environment for estimating actual evapotranspiration using the METRIC algorithm and Landsat 8 imagery. Unlike the previously developed models based on the METRIC algorithm, the selection of hot and cold pixels has been made automatic in this new toolbox. The toolbox was also used to estimate actual monthly evapotranspiration of the Urmia plain in 2016, and the results were compared with those obtained from the MODIS images to highlight the applicability of high spatial resolution imagery in water and agricultural management studies.

If the channel network map of a region is not suitable for the purpose of modeling water and solute transport processes, the underlying river network should be extracted by the relating algorithms given the critical area as the input. The goal of this study was to (1) extract the critical area in the second and third order river basins in Iran, and (2) investigate the relationship between the critical area and physio-climatic characteristics of the basins with the aim of determining the most dominant factors controlling the critical area. To this end, the closest critical area to reality was determined by minimizing the difference between the drainage density of the extracted river networks using the D8 method and the one known as the base map of the river networks. Results indicate that the spatial resolution of the digital elevation model between 30 m to 200 m does not impose significant impact on the magnitude of the estimated critical area. Also, direct relationship holds between the critical area and the soil permeability and erosion rate, while the correlation is negative between the critical area and the vegetation density. Critical area is smaller and larger in the temperate and warmer climates, respectively. Furthermore, increase in the average slope and the average annual precipitation height decreases the critical area. Nevertheless, the correlation between the critical area and the studied physio-climatic quantities is insignificant, highlighting the need to determine the critical area of a given river basin using approaches other than physical-mathematical relationships.