جستجوی مقالات مرتبط با کلیدواژه "sen’s slope estimator" در نشریات گروه "آبخیزداری، بیابان، محیط زیست، مرتع"

One of the main factors of the reducing agricultural production is the irrigation water salinity. Mazandaran province is one of the most important citrus-producing area in Iran, where the groundwater used for supplying the irrigation water in citrus orchards of the province. The main objective of this paper was to determine map spatial and temporal variations of groundwater salinity (EC) in the coastal strip of Mazandaran province with an area of 8252 km2. The collected data of 300 wells of the study area were measured by Mazandaran Regional Water Authority for 9 consecutive years and defined for ArcGIS 10.7.1 software as the average ECs for each 6 months.

EC maps were obtained by ordinary kriging (OK) for each 6-month periods from and the beginning of 2012 to the end of 2020, by using ArcGIS 10.7.1 software. According to the derived empirical function of the effect of EC on the citrus yield (Y=100-13(EC-1.4)). According to this function, ECs of 1.40, 2.17, 2.94 and 3.71 dS/m, corresponding to relative yields of 100, 90, 80 and 70% were selected, respectively. Thereby, areas belonging to the classes of 100%, 90-100%, 80-90% and <70% were outlined. In addition, the Mann–Kendall test and Sen’s slope were used to project future changes.

The result of EC maps indicated that the salinity of groundwater increases from west to east of the province. The Mann-Kendall test result showed a significant temporal trend of the size of the area below the <70% yield (EC >3.71 dS/m) and 100% (EC <1.40 dS/m), presenting that the salinity of groundwater can be a concern for citrus orchards in the coastal strip of Mazandaran province. The equation given by Sen’s slope estimator denoted that if this trend is continuing, the area under 100% yield will reach to zero in 2021 and the yield of citrus in the coastal strip will reach below 70% at the latest by 2047.

This study has shown that the salinity of groundwater was increasing in the eastern part over the time and it covered a wider area around the Miankaleh lagoon, which may be due to the leakage of the lagoon to the groundwater aquifer in that area. The reduction of groundwater quality over the time can be attributed to two factors: reduced rainfall in recent years and digging illegal wells and subsequently consumed extraction of wells in the region. Taken together, it is suggested that the wells in the area will be exploited completely controlled to prevent the reduction trend of its quality.

Investigating the climatic condition over watersheds has a decisive role in water resource management planning. Meanwhile, changes in temperature and precipitation have a great effect on the discharge of rivers, soil erosion, and fluctuations in the level of ground water, and the occurrence of floods. It is very necessary to carry out research related to climate change in order to prepare as much as possible to deal with the harmful costs caused by this change. The review of the studies conducted in Iran also shows that the scale of the study is in most cases at the local level and the study of the mean annual discharge trend and its magnitude has not been studied especially over Iran country. Therefore, the current research was planned with the aim of determining the mean annual discharge trend and magnitude over Iran. 

In the present study, the trend of mean annual discharge in Iran was determined by considering the effect of dams using Mann-Kendall and Sen’s slope methods. First, the statistics of all the hydrometric stations located in the Iran six major drainage watersheds were obtained from Iran Water Resources Management Company. Finally, 139 hydrometric stations with a statistical period of 17 to 65 years were selected in this study. The statistics of these stations were compared with the data available in nearby stations and suspicious values were also controlled. The homogeneity of the data and reconstructing the missing data was carried out using the run test and linear regression through the station with the highest correlation coefficient for each station with incomplete station, respectively. In the next step, non-parametric Mann-Kendall and Sen’s slope estimator tests were carried out within XLSTAT software in order to evaluate the trend and its magnitude analyses. After determining the trend of the study hydrometric stations, the spatial distribution map of the mean annual discharge trend in Iran six major drainage watersheds were prepared within Arc/GIS 10.2 software.  

The results showed that 14 hydrometric stations were affected by the dam. However, in the hydrometric stations without dam, 84, six and 35 hydrometric stations have a decreasing trend (60%), an increasing trend (5%), and no trend at the 95% confidence level, respectively. Examining the trend of the time series of mean annual discharge in each of Iran six major drainage watersheds also showed that 80% of the study stations in the Persian Gulf and Oman Sea watershed have a decreasing trend, while no trend were detected in 20%, 10% and 9% of the total study stations in the Caspian Sea, the Central Plateau, and the Persian Gulf and Oman Sea watersheds, respectively as well as all the stations of the eastern watershed (Hammon). In the meantime, all study hydrometric stations in Urmia Lake and Sarakhs watersheds and 68% of the study hydrometric stations in the Caspian Sea watershed have a decreasing trend. 

The results obtained from this research showed that the decreasing trend was detected in most of the hydrometric stations (84 hydrometric stations). Therefore, the decreasing trend of hydrometric stations in Iran can be related to the decrease in rainfall, increase in temperature and the emergence of excruciating droughts caused by climate changes and also human interference, including the excessive increase in the construction of dams and the change of unprincipled land use. However, one of the limitations of the current research is not taking into account climate changes and land use changes and determining the contribution of each of the mentioned factors in the decreasing and increasing trend of the mentioned stations. The results of the present research can be very useful and important for water planners and politicians in order to manage water resources.

Rivers play an important role in the economy and agriculture, but climate change and improper management have affected these resources. In order to better manage rivers, it is necessary to know their discharge trend and the factors that create the trend. The severe decrease in rainfall and the resulting dry periods have many negative effects on water resources. The continuation of droughts is a consequence of climate change. This study investigates rainfall and discharge changes in the Aras catchment located in the northwest of Iran. For this purpose, after data validation, 9 hydrometric stations and 5 rain gauging stations were selected with the statistical period of 1987-2016. The purpose of this study was to evaluate the trend of time series variations of precipitation and discharge variables using Mann-Kendall and Sen’s slope estimator tests. The results of the trend analysis showed that precipitation at two stations increased, however other stations did not experience any trends. Furthermore, there has been a downward trend in the discharge trend analysis at the six stations and no trends in the other three stations.