maysam majidi khalilabad

Groundwater level monitoring networks already exist in most alluvial aquifers in Iran. A question needs to be answered as to what extent networks are able to provide proper information about the groundwater resources to meet the water resources management objectives. Therefore, it is necessary to evaluate the efficiency of the existing monitoring network and redesign it if necessary.  This study has attempted to assess the condition of existing observation wells and the relationship between the wells and the aquifer by combining hydrogeological information and the results of a well-video inspection. Hydrogeological studies can reveal that the observation wells were drilled in which hydro-geological sequence (hydrofacies) and the external factors influence water level fluctuations. Moreover, observation well's video inspection operations, performed for the first time in Iran, can show the condition of the well casing and screen and the water-column length. The proposed framework was applied to evaluate the groundwater-level observation  well's efficiency in Shirvan alluvial aquifer in North Khorasan province, Iran. The results showed that out of 17 observation wells in the aquifer, one well is not placed into the main aquifer, six observation wells need to be rehabilitated due to screen clogging and three observation wells are at risk of going dry.

Groundwater quality degradation due to geogenic and anthropogenic factors can endanger the human health. Therefore, designing a groundwater pollution monitoring network can provide the information needed for achieving water resources management goals and improving water and food security. The main objective of this study was to introduce an integrated approach for designing a groundwater pollution monitoring network based on index-based groundwater “protection-monitoring priority” maps created with GIS. The raster layer of “protection-priority index” was prepared by combining aquifer intrinsic vulnerability maps, produced based on the DRASTIC model, and estimated groundwater value based on the quantity and quality of groundwater. Moreover, by overlying pollution-sources risk maps and capture zone maps for wells, qanats and springs, the “monitoring-priority index” was obtained. By overlying the "protection-priority index" and "monitoring-priority index" layers as well as considering the direction of groundwater flow, sampling points were determined. By applying the proposed method, 15 wells were selected for groundwater sampling in Khash-Poshtkuh study area. Water samples collected from these wells revealed that, the concentration of toxic elements such as Arsenic is higher than the permissible limit for drinking in some wells in the southeast and north of Khash aquifer and the north of Poshtkuh aquifer which have geogenic origin.

In the arid regions of Iran, the construction of Bandsar has been one of the methods of runoff harvesting. However, despite the large extent of these structures in some mountainous catchments, so far, no study has been done in Iran on the effects of mountainous Bandsars on the river flow regime and other components of the water cycle in a catchment. In the present study, the effects of mountainous Bandsars on the Marandiz river, located in the southwest of Razavi Khorasan province, and its effects on downstream water resources have been investigated. Based on field studies and satellite images more than 150 Bandsars were identified in the study area. The area of agricultural lands behind the Bandsars was determined based on satellite images, which is equal to 4.8 km2 (2.2% of the total area of the river basin). In order to estimate the runoff from rainfall on a daily basis, the Curve Number Method (SCS) was used for the period 1998-2018. The average annual runoff volume in the Marandiz river basin was estimated about 2.6 MCM and the average annual runoff coefficient was estimated as 12.4%. The minimum and maximum storage capacity of the Bandsars (SCB)were estimated to be 0.95 to 1.43 MCM, respectively. If the daily runoff volume is more than SCB, the flood can reach the watershed-outflow point and enter the downstream plain. The results showed that a maximum and minimum numbers of floods reached the watershed-outflow point were 14 (5% of days with runoff) and five floods (2% of days with runoff) during the 15-year period. Therefore, the mountainous Bandsars in the Marandiz river basin have been reduced significantly the floods entering the downstream plain which has resulted in a decrease in the downstream alluvial aquifer recharge and increasing the groundwater salinity.

Actual evapotranspiration (ET) is one of the most important and complex components of the water balance. In recent years, various remote sensing techniques and algorithms have been developed which provide a cost‐effective and reliable estimate of actual ET. In this research, the spatial distribution of actual ET at the basin scale was estimated based on SEBS algorithm and world-known information data sources which are rarely used in Iran. The estimated actual ET values were compared to the results of well-known SEBAL algorithm and the SWAT hydrological model. The study shows that the SEBS algorithm has overestimated actual ET in comparison with SEBAL algorithm. The primary cause of differences between two models is in their algorithms for calculating sensible heat. Moreover, SEBS algorithm is highly sensitive to the air temperature. SEBAL is a more complex and reliable method, but it needs reliable ground-based weather data. On the other hand, SEBS does not depend on ground-based data and its results could be acceptable under limited data condition.

Complex nature of porous media complicates any prediction of their hydraulic properties. To demonstrate shortcoming of hydraulic conductivity models predictions, the concept of tortuosity was introduced. Since there is no measured data of tortuosity, and tortuosity has a direct relationship to hydraulic conductivity, so in this study we aimed to develop a general mathematical relationship to determine tortuosity. An optimization code were run in MATLAB R2014a software, using Monte Carlo algorithm, aimed to minimize Root Mean Square of Logarithmic Deviation (RMSLD) between calculated hydraulic conductivity values based on Shepard (1993) and van Genuchten (1980) models, to determine tortuosity on different water contents for 69 soil samples of UNSODA database with a wide range of soil textures. Considering fractal concepts, we developed a linear equation empirically to determine hydraulic tortuosity as a function of effective saturation, pore fractal dimension, porosity, inverse of air entry pressure and soil water content, covering whole ranges of degree of saturation. Based on results, calculated values of tortuosity were greater than proposed values by Shepard about 30%. To evaluate developed equation, statistical parameters of Root Mean Square of Logarithmic Deviation (RMSLD) and Akaike’s Information Criterion (AICc) was adopted for 17 different soil samples. According to the calculated statistical parameters, using developed equation to estimate tortuosity has improved the results of Shepard’s method significantly. Totally, the results show that, despite the developed equation has a relatively complicated structure, in terms of the compromise between accuracy and complexity has an acceptable performance.

In the last decade, various aspects of groundwater resource depletion have gained a special place among water sector experts and decision makers. Research in this area is relatively new in most parts of the world. Groundwater depletion, which has been in a concerning state for most plains in Iran in recent years, has various consequences which impede sustainable development. One of the most important consequences of the dropping groundwater table is its impact on the economy of the agricultural sector. A problem that, despite its obviousness and bi-directionality, has rarely been quantified. In this research, it is attempted to simulate the status of groundwater resources under the influence of continued groundwater overdraft until 1420 (2041), on the basis quantitative (harvestable water) and qualitative (electrical conductivity) effects on the economic status of agricultural sector using cultivation area indices. We examine agricultural products, their performance, farmers’ income, and labor force. Questionnaires were used to estimate costs and incomes and the results of combined modeling of surface and groundwater in Neishaboor plain were used to estimate the amount available water. The model predicted a decrease of up to 24 m in water table and an average increase in salinity of 5500 mmhos/cm for the Neishaboor plain. The effects of the occurrence of these events was then modeled. Based on models for cropping patterns, water-yield equations, and salinity patterns, we estimated a 30% reduction in area under cultivation, a 65% decrease in crop yields, and a 28% decrease in labor force by 2041. Over the next 20 years, these impacts will significantly reduce revenues in the agricultural sector in Neishaboor plain, which will pose important secondary problems and consequences.