جستجوی مقالات مرتبط با کلیدواژه « آبیاری » در نشریات گروه « زمین شناسی »

In this study, the hydrogeochemical and qualitative status of groundwater resources of the Zarabad coastal aquifer in southeast Iran has been investigated. The decreasing order of cations and anions is Na+>Ca2+>Mg2+>K+ and Cl->SO42->HCO3-, respectively. The two most water type are Na-Cl (78%) and Ca-Mg-Cl (22%). The water type, chlorine-alkalinity index, ion ratios, and position of the samples on the Gibbs diagram show that cation exchange (direct and reverse), weathering of silicates and evaporites, and seawater intrusion are the main controlling processes of water chemistry. The ionic ratios of SO42-/Cl-, B/Cl-, and Na+/Cl- indicate that saltwater infiltration increases as the distance from the Rabach River increases, particularly in the northwest and southeast regions. This can lead to a decrease in the quality of water resources. Moreover, the water quality for agricultural use is assessed based on some indices, including electrical conductivity (EC), sodium percentage (Na%), sodium absorption ratio (SAR), residual sodium carbonate (RSC), magnesium absorption ratio (MAR), permeability index (PI), Kelly’s ratio (KR), and USSL and Wilcox diagrams. The results showed that about 60% of the samples had unsuitable quality for irrigation. These samples were located in the northwestern and southeastern parts of the plain. About 40% of the samples have suitable quality for irrigation and are located in the vicinity of the Rabach River.

Nowadays one of the key factors controlling development of sustainable agriculture is unsuitable quality of irrigation water. The use of unsuitable water for agriculture could cause some problems regarding salinity, infiltration and toxicity. The aim of this study is to predict the spatial distribution pattern of groundwater quality indices for agricultural purpose in Golestan province. The spatial variability of EC, TDS, SAR, pH, Na, Cl-, SO42-, Ca2, HCO3-, Na%, ES and PS of water samples obtained from 207 observation wells was investigated. The experimental semivariogram of all parameters was calculated and the best theoretical model was fitted. Ordinary kriging is then used to interpolate the values of investigated parameters at unsampled locations and their spatial distributions were mapped through GIS. The probability maps of exceeding a given critical threshold were produced for some parameters and indices using indicator kriging. The results showed that all water quality parameters have good spatial autocorrelation with spherical structure. Using the generated estimation maps the study area was classified into different water quality zones considering US soil salinity laboratory as well as FAO standard for irrigation. Based on US soil salinity laboratory, 95% of the study area has a moderate water quality (C3S1 and C3S2). Based on FAO limit, 89% of the study area has good and moderate water quality. The area with appropriate water quality is about 2592 sq km mostly contains eastern, southeastern and northwestern parts of the study area. Moreover based on the probability maps of ES and PS, there is a higher probability of salinity risk in central regions as well as some parts in west. The generated estimation and probability maps can help decision-makers and planners to make proper decisions for appropriate use of soil and water resources and development of a sustainable agriculture in the region.