نشریه مدل سازی و مدیریت آب و خاک
سال دوم شماره 2 (تابستان 1401)

The study of changes in precipitation and temperature components provides the basic information needed to assess the frequency and severity of climatic and hydrological processes. Therefore, the present study investigates the temporal changes of precipitation and temperature at different time scales in Karkheh Watershed. The present results are applicable in regional planning and decision makings.

Karkheh Watershed with an area of 51337 Km2 located in the west and southwest of Iran includes Kermanshah, Hamedan, Kurdistan, Ilam, Lorestan and Khuzestan provinces. The average annual rainfall in Karkheh Watershed varies from 150 mm in the southern regions to more than 1000 mm in the eastern regions. To do this study, daily minimum and maximum precipitation, temperature and sunny hours of six synoptic stations of Ahvaz, Dezful, Hamedan, Khorramabad, Kermanshah and Sanandaj in Karkheh Watershed with the statistical period 1980-2010 were used. The trend of changes in time series of precipitation and temperature was evaluated using Mann-Kendall statistical test and age estimator.

The results show that in the case of precipitation, the changes in most stations are decreasing and without a significant trend, and in a limited number of stations it has a significant decreasing trend, which is generally related to the cold months of the year (-0.09 and -0.07 at the station). Khorramabad and Sanandaj in February). The most changes in precipitation trend were observed in annual time series (-0.02 in Sanandaj Station). Thus, in most stations, a significant decrease in precipitation is observed. In all time series, the minimum and maximum temperatures in most stations have an increasing trend. The rate of this increasing trend is higher at minimum temperature (slope of changes 2.77 and 2.75 in Sanandaj and Ahvaz stations, respectively).

Analysis of daily, monthly, seasonal and annual trends of precipitation and minimum and maximum temperatures in the period 1980-2010 are very important due to their high impact on the hydrological response of watersheds as well as environmental issues. Also, the role of climate change and its effects on the trend of marginal phenomena in different regions can have many consequences. The present study was conducted to investigate the trend of precipitation and temperature in different time series. The results of the analysis of the monthly rainfall trend in the study period showed a decreasing and insignificant trend in most stations and in most months. Also, in most of the study stations, the monthly minimum temperature, with the exception of January, November and December, has an increasing trend and indicates that the monthly minimum temperature in the Karkheh Watershed has been increasing in recent years.

Drought occurs due to lack of humidity and deficiency in precipitation amount. Therefore, it is important to recognize and investigate the effective factors on precipitation deficiency and consequently drought occurrence. Enso is a phenomenon of climatic teleconnection that can affect weather in different regions of the world. Enso is one of the important large-scale phenomena affecting the temporal and spatial distribution of rainfall and consequently the drought that occurs in the tropical Pacific. The objective of this research was to investigate the effect of Enso on meteorological drought in the midwest of Iran.

First, precipitation data of synoptic stations in 14 locations were obtained in the west of Iran. Then, SPI values was calculated at different time scales of 1, 3, 6, 9, 12, 15, 18, 24, and 48 month using the spi-sl-6.exe software package. In the next step, using the data of Enso including Nino1+2, Nino3, Nino3.4, and Nino4, the Spearman correlation test was simultaneously performed in the Minitab16 program. Then, the asynchronous relationship was investigated with the cross-correlation function between Enso and SPI in time series of months 1 to 48 in SPSS16. Finally, linear regression modeling was performed. Multivariate regression test with simultaneous and delayed states of 1-6, 12, 24, and 48 months was used based on the stepwise method.

Results are presented in three sections: simultaneous, asynchronous relations, and regression equations. Results showed a high correlation between seasons of autumn and spring with indices of Nino4, Nino3.4, Nino3, and Nino1+2. In addition, the asynchronous relationship was better than the simultaneous mode. Better significance in the asynchronous mode is due to the effect of Enso on weather and drought in Iran. Considering the p-value <0.05, it was shown that the highest significance was observed between Enso indices and drought index in Bushehr station. In addition, in a number of stations, including Arak, Urmia, Shiraz and Hamedan, no significant relationship was observed in their simultaneous state. The regression analysis showed that Nino4, Nino3.4, Nino3 and Nino1+2 indices had the highest effect in different time series of SPI with the highest positive and negative coefficients of atmospheric oceanic index in all stations. The results showed that high correlation between Enso and SPI can affect predicting climatic conditions, drought, floods, planning, and crisis management in watershed scale.

Enso can be used as predictors of long-term climatic factors such as precipitation and temperature. Enso phenomenon in Nino1 + 2, Nino3, Nino3.4 and Nino4 regions can be used as predictors of climatic factors such as rainfall for long-term forecast of precipitation and finally drought and wet season in different parts due to the universal Enso phenomenon. It seems that due to the mechanism of the Enso phenomenon and its relationship with natural disasters, further studies can be effective in predicting climatic conditions, drought and floods in Iran which ultimately can be used in predicting hydro-climatic events.

The reduction of groundwater level in the plains of Khorasan Razavi Province has caused the destruction of groundwater quality and salinity of water resources. This has happened more intensely in Mehvalat plain. Since groundwater in this plain is often used for agriculture and drinking, so knowing the quality of groundwater for use in these two sections is important. Therefore, the purpose of this study is to evaluate and zone water quality variables for two types of drinking and agriculture consumption.

PH, permeability index (PI), sodium absorption ratio (SAR), and electrical conductivity (EC) variables have been selected to evaluate the water quality suitable for agriculture and irrigation. Also, the quality of drinking water was compared with the international and national standard indicators. Spatial interpolation methods are now widely used to monitor spatial variations in water quality. In order to zone water quality parameters, a kriging method that is preferable to other geostatistical methods was used.

SAR in irrigation water can be used as an indicator to determine the risks of soil sodium contamination. This index was studied for Mehvalat-Feyzabad water wells and is in the middle range. 68% of the study area is in the appropriate class in terms of irrigation water PI and 32% is in the relatively suitable range and no points were found in the inappropriate class. According to the spatial zoning map, pH is in the allowable range of 7 to 8.5 and the EC of water is in the range of low salinity to very saline. The best EC linear relationship with cations, anions, and TDS (Total Dissolved Solids) was presented for the study area in this study. Examining the relationship between these three variables shows that the increase in EC indicates an increase in the amount of cations, anions, and TDS and will affect the consumption of this water for agriculture and drinking in the future.

Due to the fact that the salinity of water for agricultural use was assessed from low salinity to very saline, so leaching and drainage should be done and the type of cultivation should be selected according to the salinity. For areas that are in the very saline group, it is necessary to use salinity-resistant plants with good drainage and low planting frequency. Examination of drinking water quality in the area showed that its use is not suitable for drinking.

Precipitation deficiency, its uneven spatio-temporal distribution, groundwater decline, and water loss in traditional irrigation systems, make it necessary to introduce appropriate solutions to improve the soils in arid areas. Meanwhile, the optimal use of rainfall, should be a priority in water-scarce areas. Achieving these objectives can be an effective factor in reduction of irrigation costs in planting projects in desert areas. The effect of these supplements on plant traits has been less studied. In this regard, the effect of Abyar and Absar irrigation supplements on the amount and duration of irrigation and soil properties of planting areas has been investigated. Therefore, this study investigates the efficiency of different concentrations of two irrigation supplements on some morphological characteristics (plant traits) of A. canescens in vitro conditions.

A completely randomized design with three treatments and three replications at concentrations of 1:1000, 1:2500 and 1:5000 in a five-months period under greenhouse conditions. In addition, the structural and biomass traits of aerial and underside of A.canescens rootstocks were measured in different treatments. At the end of the research period and removal of seedlings from the soil, plant traits of aerial parts and subsurface, including; shoot length, shoot weight, shoot dry weight, and increase shoot height and root length, root weight and root dry weight were measured for each replication. The statistical analysis was performed by using Duncan test.

The results showed that the effect of supplements on root length and fresh and dry weight of the plant was not significant. Based on the results, the effect of supplements on root width was increasing and had a significant effect at 95% confidence level. the effect of supplements on the length, weight and dryness of the shoot was significant and increasing. However, the effect of supplements on increasing the height of the aerial part was significantly reduced at 95% confidence level. Overall, an increase in the concentration of the supplements showed a negative effect on the structural and biomass traits of aerial and species. Therefore, the use of irrigation supplements with low concentrations (1:1000 and 1:2500) for structural and biomass of A.canescens transplants is recommended in greenhouse conditions and before their transfer to the natural environment.

The use of Abyar & Absar, has negative effects on the structural and biomass traits of aerial parts and root of A. canescens. Also, it had a significant effect on root width only among root characteristics. The effect of supplements on the amount of root length and their wet and dry weight was not significant. The effect of supplements on the width, length, weight and dryness of the shoot was significant and increasing. It is suggested to investigate the effects of irrigation supplements on plant traits and characteristics of different species in different field conditions as well as other concentrations.

Sediment Production in catchment area subject to very much factors, the one of these factors are not correct use of the lands. Environmental characteristics such as amount and intensity of precipitation, the degree of slope and accumulation of aqueducts in production of runoff and sediment is effective. Sediment production in a watershed depends on several factors, one of the most important of which is inappropriate and unprincipled use of lands. Different environmental issues also have different effects on sediment production. Aghajari formation consists of gray and brown calcareous sandstone, gypsum red marl, and siltstone. Its main section spreads from Omidiyeh to the Aghajari oil field and it has a thickness of 2965 meters. Gahsaran formation has a thickness of about 1600 meters. A viewpoint of lithology is consisting. Statistical studies in the mentioned regions show that the absolute maximum air temperature is 46 °C, the absolute minimum temperature is -6.7 °C and the annual temperature average is 20.8 °C. The annual rainfall average is 636 mm.

In order to investigate sensitivity to the erosion and sediment yield the various land uses of Aghajari and Gachsaran deposits, part of Margha and Kuhe Gach watersheds areas in Izeh Township was elected. This investigation to determine productivity runoff and sediment in 6 points and three times replicates in Gachsaran formation and in 7 points and with three times replicates in Aghajari in the various intensities of precipitation 0.75, 1, and 1.25 mm in minute in three land uses range, the residential and agricultural lands to help kamphorst rain simulator do. These experiments were carried out in Aghajari and Gachsaran formations at the end of spring and after harvesting in agricultural lands, and in order to create homogeneous conditions for rainfall simulation, there was no vegetation at plot level in Aghajari and Gachsaran formations. In this study, samples were randomly identified and harvested. Also, all information related to different studies in the studied watershed including climate and geology were used in this study. Spss and Excel software were used to perform all statistical analysis.

Comparing runoff and sediment in two formations showed that in the low intensities of precipitation formation type in runoff and sediment has more interference. Whatever precipitation increases, the difference to at least it seems. It is also recommended that due to the high erosion and sedimentation of these two formations, reservoir of large dams is not located in these two formations because at a very short distance or the reservoirs of these dams are filled with sediment. Or they become so salty that they cause huge damage to downstream areas or cause dangerous landslides in the dam reservoir, which will eventually lead to dam breakage and ultimately devastating floods by pushing large volumes of water into the dam body.

In addition, research results showed that erosion and sediment rates in land uses of Gachsaran formation is more than Aghajari formation land uses due to Ec and more distance gypsum hardpan than soil surface. However, two formation of viewpoint run off rates proximately had similar trend. The results also showed that due to high erosion and sedimentation of these two formations, reservoir of small and large dams is not located in these two formations.

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.

The phenomenon of climate change and global warming is one of the biggest challenges of the present age, which has affected the hydrological cycle on a global and regional scale. The purpose of this study is to investigate the effects of climate change on torrential rains And Temprature, Rainfall, Run off  in Tehran province. In this study, changes in torrential rainfall in Tehran and the frequency and intensity of torrential rainfall in the future and climate change and the rate of increase of floods on periodic floods have been investigated.

This research has been done in two study discussions (meteorological, hydrological). First, parameters (temperature and precipitation) for synoptic stations (Abali, Shemiran, Mehrabad) for the period (1988-2020) were received from the Meteorological Organization and rainfall and runoff data from hydrometric stations were received from the Tehran Regional Water Authority. Down Scaling model and methods in this research SDSM-DC, Mann-Kendall, Rclimdex, XLSTAT, to simulate future floods and SMADA, HEC-HMS model to simulate floods in current and future periods have been used.

The results showed that the temperature extreme indices in all stations had an increasing trend and the precipitation indices had an increasing trend only in Abali station. But rainfall in Shemiran and Mehrabad stations had a decreasing trend. Examination of rainfall changes using Mann-Kendall test in most months of the year shows a stable trend and jumps are observed in the rainy months, which can be justified by the increase in rainfall frequency. In the CanESM Model 2 simulation, emphasizing the RCP8.5 release scenario, an increasing temperature trend was observed for the coming decades. The highest temperature increase belongs to Mehrabad station with an average temperature increase of 5.1 percent for the period 2021-2083. The highest rainfall for all three stations is estimated in March next year. Therefore, with the increase of temperature trend, changes in the type of precipitation have occurred, which can be affected by urban microclimate. Simulation of the rainfall-runoff model of the basin with the HEC-HMS model showed that the volume of discharge in the future will be reduced by 5 percent and for return periods, the maximum discharge is estimated at 1501.7 cubic meters.

Due to Rainfall behavior is expected to increase in the coming decades, while reducing its fluctuations. It is predicted that the climate of Tehran in the future will have more fluctuations in precipitation and warmer than the current situation, and this increase and frequency of precipitation is likely to increase flood frequency and reinforce its occurrence, while rainfall will occur more accidentally but with greater intensity, leading to environmental and urban hazards.