جستجوی مقالات مرتبط با کلیدواژه « تغذیه آب زیرزمینی » در نشریات گروه « آب و خاک »

The sustainable availability of water resources and the qualitative and quantitative status of these resources are threatened by many natural and antropogenic factors, among which climate change plays an important role. Climate change can have profound effects on the hydrological cycle through changes in the amount and intensity of precipitation, evapotranspiration, soil moisture, and increasing temperature. On the other hand, the distribution of rainfall in different parts of the world will be uneven. So that some parts of the world may face a significant decrease in the amount and intensity of precipitation, as well as major changes in the timing of wet and dry seasons. Therefore, sufficient knowledge about the effects of climate change on hydrological processes and water resources will be of particular importance. In this research, as the first comprehensive study, the effect of future climate change on the water resources components of Neyshabur-Rookh watershed was investigated by a set of one hydrological model and six General Circulation Models under the RCP4.5 scenario.

The Neyshabur-Rookh watershed with an area of 9449 square kilometers is a sub-basin of Kavir-e Markazi-e Iran and a part of the Kalshoor Neyshabur watershed, which is located between of 58 degrees and 13 minutes and 59 degrees and 30 minutes and east longitude and 35 degrees and 40 minutes and 36 degrees and 39 minutes north latitude. The study area with an average altitude of 1549.6 m above sea level and average annual precipitation of 246.83 mm, a mean annual temperature of 13.3 Celsius has an arid to semi-arid climate. For hydrological simulation of the watershed using WetSpass-M model, maps of Digital Elevation Model (DEM), land-use, soil texture, slope, and distribution map of groundwater depth, Leaf Area Index (LAI), and climate data (rainfall, mean temperature, potential evapotranspiration, wind speed and the number of rainy days) per month in 1991-2017 period were used. Then the prepared model was calibrated and validated. The climatic data of six General Circulation Models (GCMs) under the RCP4.5 scenario (Representative Concentration Pathways) were downscaled using the Quantile Mapping Bias-Corrected method. The downscaled GCM models were ranked and weighted in each station according to results of the Leave one out cross validation method and utilized as an ensemble for projecting the near-future climatic conditions of the water resources components of the watershed. By importing the monthly maps of precipitation, average temperature and evapotranspiration in the period of 2026-2052 into the calibrated hydrological model, the hydrological response of watershed to near future climate change was determined and evaluated.

WetSpass-M was calibrated by changing the calibration parameters in five hydrometric stations and the compared measured and simulated streamflow. The values of four evaluation criteria NS, R2, MB, and RMSE indicated the good performance of the model during the calibration and validation process. By predicting climatic parameters in near future and preparing and importing maps of monthly precipitation, mean temperature, and evapotranspiration to WetSpass-M, the hydrologic simulation of the watershed was done in the 2026-2052 period. The results indicated that the mean annual temperature and precipitation would be respectively increased by 4.66% and 1.21°C under RCP4.5 in the near-future period compared to the baseline period. The average temperature will increase in all months so that the most changes will occur in September and the least changes will occur in March. The rainfall of the watershed will increase in March, April, May, October, and December and will decrease in the rest of the months. The highest and lowest rainfall changes will happen in April and August, respectively. The analysis of the components of water resources in the near future shows that annual total runoff, groundwater recharge, and actual evapotranspiration will increase by 5.9%, 14.85%, and 1.42% compared to the base period, and annual direct runoff and interception will decrease by 15.15% and 3.54%, respectively.

Considering the importance and major role of the Neyshabur watershed in the economy of agricultural products of Razavi Khorasan province, the results of this research will be of great help to the managers and policymakers of the country's water resources management in order to make appropriate decisions with the aim of reducing the effects of climate change on the water resources of the Neyshabur-Rookh Basin.

Estimating groundwater recharge using other affecting factors such as hydro-meteorological, and physical factors, is the main way to understanding, predicting the sustainability and availability potential of aquifers. The objective of this research was investigating the efficiency of some individual and ensembled models and the effect of the ensembling on promoting the efficiency of Bayesian and Random forest models.

The required environmental layers (DEM, aspect, slope, curvatures (profile and plan curvature), lithology, landuse, soil texture, NDVI, fault distance, river distance, SPI, drainage density, TWI), were prepared by ArcGIS 10.6 software for the study area. the Bayesian theory and Random Forest models and ensembling of these models were avaluated. To consider the ensemble effect of these models, input layers were used in two models and then the models were ensembled by several scenarios, which were based on the principles of basic mathematics. The double-ring infiltrometer method were used for understanding the spatial variability of groundwater recharge potential (GWRP). The performance of the models was evaluated using statistical measures. ROC, CCI, and TSS indices were used for evaluating the results of implemented models. Finally, GWRP mapping prepared and the percolation of the study area was classified into five classes: very high infiltration, high infiltration, medium infiltration, low infiltration and very low infiltration.

The sandy-clay-loom soil texture and the Quaternary sediments (Qft2), rangeland and agriculture areas (in landuse layer), showed maximum percolation. The results indicated that the random forest (RF) model was identified as the superior model compared to Bayesian and ensembled models, by ROC, TSS and CCI indices (ROC= 0.983, TSS= 0.86, and CCI= 93.9, respectively). Also, among the ensembled models, the RFBa5 model (based on the fifth scenario) was evaluated as the most efficient model through ROC, TSS, and CCI indices (ROC= 0.984, TSS= 0.76, and CCI= 87.94, respectively). Based on the first individual model (RF), 11% of the study area had moderate to very high infiltration potential. This despite the fact that the 89% of the study watershed was found with low and very low potential. While according to RFBa5, 30% of the study area were estimated with moderate to very high potential and 70% with low and very low potential. The Bayesian model was observed as the weakest model. But based on the ensemble of this model with the random forest model, under different scenarios, the strengthening of this model was observed. These results show the positive effect of ensembling the models.

The GWR potential maps are useful in planning with more accuracy for implementation of artificial GWR, soil protection, aquifers and watershed management projects in order to protect water and soil resources by directing runoffs to preventing the soil erosion and aquifers recharge. It is recommended to study different suitable models and their ensembling in this field or other watersheds and select the best model to get the best performance and obtain an accurate map.

Understanding water budget components is crucial for making decisions regarding water resources planning and management. Surface water–groundwater interactions are commonly investigated at the river reach scale and generally classified as connected or disconnected type systems. Connected systems are either gaining surface water system, where groundwater discharges through the streambed to contribute to streamflow, or losing surface water system which loses (or recharges) water to the local groundwater system. Disconnected systems are defined by an unsaturated zone beneath the surface water system which loses water at a rate related to the hydrogeological properties of the streambed and the aquifer. These interactions have significant implications for both water quantity and quality. Seepage of fresh groundwater into a river can be important in maintaining flows during extended dry periods. This can be critical for supplying the needs of surface water users such as irrigators as well as for aquatic ecosystems. Pumping from an aquifer near a river can dramatically change the amount of this base-flow to the river. In contrast, if the groundwater is contaminated, increased groundwater discharge can have a negative effect on river water quality. The Bojnourd catchment is located in North Khorasan province. The catchment covers an area of about 1265.8 km2. The main river in this area, Firouze River, is approximately 10 km in length, and is hydraulically connected to the Bojnourd alluvial aquifer. The alluvial aquifer of Bojnourd plain with 65.2 km2 area is mostly covered by urban area. Hence, effective management of water quantity and quality issues in the Bojnourd catchment requires quantifying flow between surface water and groundwater. Furthermore, conveying water from the outside of basin caused water table to rise which made some problems for urban buildings and infrastructures. Therefore, the river and aquifer interaction needs to be studied more comprehensively.

Numerous techniques and methods are available to describe and quantify the flow between surface water and ground water. This study combined two methods, numerical modeling using MODFLOW code and reach measurements, to quantitatively evaluate groundwater/surface water interactions under highly transient conditions. The groundwater flow system of the study area was conceptualized based on borehole logs, pumping tests, and available hydrogeological and geophysical information. Moreover, field work, including measuring streamflow in three seasons, was carried out to conceptualize and quantify the groundwater/surface water interactions. Following the conceptual model, the numerical model was developed to simulate flow through the system. The model grid had 1274 active cells with a uniform cell spacing of 250×250 m. The water exchanges between the main regional river, Firouze river, and Bojnourd aquifer was simulated using the River (RIV) package. Both hydraulic head target and flux target were used to calibrate the model. The head targets were compiled from the monitoring network which contains 11 observation wells. The flux targets were located in three measurement points along the Firouze river. The data obtained from the fieldwork were used as observed values for the groundwater/surface-water exchanges. The transient model was calibrated and validated for 15 hydrological years, i.e. from 1 October 2001 to 1 October 2016

Model performance was evaluated using root-mean-square error (RMSE). The model results were in agreement with corresponding observed data, including groundwater heads and measured groundwater/surface-water exchanges. The RMSE values during calibration and validation periods were 0.83 m and 1 m, respectively. Analyzing water balances resulted from transient simulation showed that Firouze river is gaining in some reaches and losing in other reaches. In losing reaches, the total flux into the aquifer is 6.4 MCM per year. In gaining reaches, the volume of groundwater discharges through the streambed is about 4 MCM per year. Furthermore, the effect of several management scenarios, including continuing the existing condition, turning the domestic wells off and implementing a sewage system by 2025, on groundwater heads and groundwater/surface-water exchanges was examined using the numerical model. Results showed that by implementing the sewage system, the volume of water discharged to the river would decrease, but it will prevent aquifer and river contamination caused by sewage water. 

In this study, groundwater budget components in Bojnourd aquifer including groundwater/surface-water exchanges were calculated. The results showed that understanding of these surface water-groundwater interactions, which has been ignored in previous studies, is important for effective management of water quantity and quality issues in Bojnourd plain. Moreover, the methodology used in this study including numerical modeling and measuring flow at multiple points along the stream is effective and easy to apply to estimate the direction and magnitude of seepage on a stream reach basis.

Today groundwater resources play an important role in the water supply of agriculture. Iran is in the semiarid region so evaluation of irrigation that turns into groundwater resources that called the return flow could have a major role in groundwater recharge and must be considered for effective management of groundwater resources. The goal of this study was investigating the effect of irrigation on groundwater recharge by using the HYDRUS-1D model. In this case study, the data were obtained from a complete growing season of maize and wheat which were planted in the Hashtgerd Alborz Province during the years of 20004 2013. Soil moisture and deep percolation were simulated for two different irrigation efficiencies of 60 and 80 percent (equivalent to 40 and 20 percent deep percolation of irrigation, respectively). The results showed that soil moisture advance underirrigation efficiency increased the level of ground water to 1 m. Also the highest percentage of groundwater recharge from irrigation and rainfall was for winter wheat. During the simulation, irrigation efficiency of 60% and 80%, recharge 2.63 m and 1.6 m the ground water level that 14.6 and 10.92 percent are included irrigation and rainfall respectively. The results of this study showed that deep percolation of irrigation and rainfall can recharge and rise of the groundwater level.

For sustainable use and vulnerability assessment of aquifers, the groundwater recharge estimation is necessary. In Iran where located in a semi-arid region, the groundwater recharge is closely dependent on the return flow from irrigation. Therefore, determining the proportion of the return flow in recharge from different irrigation methods is essential for better management of groundwater resources. In this study in Neyshabour watershed, the recharge amount of two different irrigation methods (furrow and sprinkle irrigation) were estimated using soil moisture measurement in 2 wells of a wheat farm with 6 meters depth. In each well, the REC sensors were installed with 0.5 meter intervals and two sensors were also installed in 0.15 and 0.3 m depths. Using these sensors, the soil moisture was daily measured during 173 days. Then these values were used to simulate the unsaturated flow in these points using the 1D HYDRUS package. The model in each point was calibrated and implemented to estimate the drainage amount underneath the 6 meter depth soil layers. The drainage amount from 6 meters soil layer during 173 days in the furrow irrigation was 80 mm and in the sprinkle irrigation was negligible.

Hamedan-Bahar plain is one of the groundwater restricted areas. The excessive groundwater extraction has led to significant drop in water table in the past three decades. Therefore، in this study water extraction from groundwater resources was calculated. Then، the amount of groundwater recharge was estimated based on the type of crop and irrigation system. Data from 2132 groundwater wells of Hamedan - Bahar plain during the years 2008 to 2009 was collected. The ArcGIS 9. 3 software was also used to find the spatial distribution of rainfall، the amount of runoff and the relevant groundwater recharge rate. The results showed that the groundwater recharge volumes were 96. 08، 41. 02، 76. 01، and 55. 8 million cubic meters and also the groundwater extraction volumes of the aquifer were 112. 6، 143. 7، 31. 5، and 7. 04 million cubic meters for spring، summer، autumn، and winter، respectively. In summer، the groundwater extraction rates at 15. 27 and 21. 69 percent of the plain،s area were five times and about three to five times more than the groundwater recharge rate، respectively. In spring، the groundwater extraction reate at the 3. 2 percent of the plain area was about three times more than the groundwater recharge and the groundwater extraction at 35. 55 percent of the plain area was about one to three times more than groundwater recharge. In autumn، the groundwater extraction rates at 0. 66 and 8. 88 percent of the plain area were three times and about one to three times more than the groundwater recharge rate، respectively. In winter، the groundwater extraction at 0. 54 percent of the plain area was three times more than the groundwater recharge and the groundwater extraction at 2. 08 percent of the plain area was about one to three times more than the groundwater recharge.