Irrigation
Ramin Fazloula; Hedyeh Pouryazdankhah
Abstract
IntroductionMazandaran province is one of the most important rice and citrus-producing areas in Iran, where most of the citrus orchards and agricultural fields are irrigated with groundwater. On the other hand, irrigation water pH is one of the basic qualitative factors that determine the solubility ...
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IntroductionMazandaran province is one of the most important rice and citrus-producing areas in Iran, where most of the citrus orchards and agricultural fields are irrigated with groundwater. On the other hand, irrigation water pH is one of the basic qualitative factors that determine the solubility and biological availability of chemical components in the soil such as nutrients and heavy metals, and it can affect agricultural production.Materials and MethodsThe coastal strip of Mazandaran Province toward the southwest of the Caspian Sea is situated in the north of Iran with an area of 8,252 km2 between 35.77 to 36.99 N latitudes and 50.36 to 57.13 E longitudes. In this study, the temporal and spatial variations of groundwater salinity were studied in the coastal strip using data from 300 wells, collected by Mazandaran Regional Water Company. Data included mean pH for each 6-month period of 9 consecutive years, from 2012 until the end of 2020. pH maps and maps of the risk probability area for rice and citrus growth were obtained by using Ordinary Kriging (OK) and Indicator Kriging (IK) in ArcGIS 10.7.1 software, respectively. Classifications were selected according to the properties pH range for the growth of citrus (5.8, 8) and the optimum pH for rice (6.8) in OK method. The indicator amount of pH was considered equal to 6.8 in IK method. Thereby, areas belonging to different pH classes were outlined and places with the risk probability for growing the rice and citrus were identified.Results and DiscussionThe 11 different models for semivariograms were drawn, and the best one was chosen according to the lowest nugget-to-sill ratio, and thus Stable and Exponential were obtained as the highest frequency for first and second half-years. The indices of cross validation for each selected semivariogram were estimated within acceptable ranges. In Ik method, the pH of studying area was classified into 4 ranges of <5.8, 5.8–6.8, 6.8–8.0, >8, and the percentage area of each classification derived from the ArcGIS software, the average area of each classification during the studying period was calculated zero, 0.6, 83.5 and 15.9 percent, respectively. It showed that most part of the study area located in the range of 6.8-8. It means most rice fields and citrus orchards were irrigated by the groundwater with the pH close to neutral. The obtained maps in the OK method indicated that the pH of the groundwater was not acidic in any points and alkaline conditions were observed in the western and eastern parts of the province. Therefore, The IK method was used to further investigate and determine the vulnerable areas. The probability of pH risk in rice and citrus growth was classified into 4 ranges (0-20%, 20-40%, 40-60% and 60-100%), and the average percentage area of each classification along the period was estimated 94.9, 4.8, 0.3 and zero percent, respectively. Using the IK method, higher probability of groundwater pH reducing the yield in citrus orchards and rice fields was found in eastern parts of Mazandaran province, which was about 5% of total studying area. Also, the results of the study in these 9 consecutive years did not show any decreasing or increasing trend in pH changes and consequently the area under each classification.ConclusionGenerally, the results indicated that the pH of groundwater for irrigating the citrus orchards and rice fields was appropriate in the most parts of the province and merely in the eastern part of the province, low water alkalinity may make a risk probability for rice and citrus growth in both western and eastern parts of the province. Due to the fact that alkaline water causes soil alkalinity and consequently reduces the solubility of phosphorus and some other plant nutrients in soil, it is suggested to supply the optimum required fertilization amounts of the nutrients in soil. However, the amount of fertilization should be on the basis of field research results. It is also proposed to study the condition of rice and citrus growth and the irrigated water in more details through the farms of western parts of the province. Due to the fact that most citrus orchards in this province are irrigated under the pressurized irrigation systems and using groundwater for irrigation, it is suggested that the Langelier Saturation Index (LSI) be examined in future research.
Mina Touzandejani; Alireza Soffianian; Norollah Mirghafari; Mohsen Soleimani
Abstract
Introduction: All living organisms, such as plants, animals and humans depends on the water and life may exist in a place where water is available. Groundwater is the main source of drinking water for more than 5.1 billion people around the world, especially in arid and semi- arid regions such as Iran. ...
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Introduction: All living organisms, such as plants, animals and humans depends on the water and life may exist in a place where water is available. Groundwater is the main source of drinking water for more than 5.1 billion people around the world, especially in arid and semi- arid regions such as Iran. Currently, groundwater provided about 60 percent of the worlds drinking water and 77.8 percent of the Iran's drinking water. In recent years, it has been found that groundwater quality is also important as much as its quantity. Nowadays, pollution of groundwater resources from pollutants, especially heavy metals reduces the quality of these resources. Heavy metals are one of the most important environmental pollutant that its entering into the water is raised by agricultural activities, industrial and urban development. Among the heavy metals, arsenic is a toxic and carcinogenic metalloids which are widely distributed in the environment and it has a twentieth abundance of elements in the Earth's crust with an average of 1.8 mg kg-1. Arsenic has been classified in the first group of cancer-causing compounds. It has different effects such as horny skin, liver, skin and bladder cancer, mental disorders, damage to neurons, blood pressure, lower IQ and reducing white blood cells and red blood. The Maximum permissible arsenic in drinking water is 10 micrograms per liter which has been identified by the World Health Organization and America Environmental Protection Agency. According to national standards of Iran, limitation of arsenic in drinking water is 10 micrograms per liter. So far, numerous studies were done to evaluate the environmental contamination of heavy metals, especially arsenic using geostatistical methods. The aim of this study was to evaluate the quality of groundwater in terms of Arsenic pollution.
Materials and Methods: study area is Hamedan - Bahar aquifer with an area of 800 square kilometers that is located on the northern slopes of Alvand Mountains. The central part of Hamadan city, Lalejin, Saleh Abad and Bahar city is located in the study area. To conduct this study, concentrations of arsenic was investigated in 94 groundwater points. To determine the spatial distribution of arsenic, different geostatistical methods were used. Then the results of this methods were compared using cross validation technique and MAE & MBE index and the most suitable method was chosen for this purpose. Eventually RBF method by multiquadric model was used. Moreover Contamination probability map was developed using indicator kriging models.
Results and Discussion: Arsenic concentrations were in the range between 5 – 79.5 micrograms per liter. Also The average concentration was 12.4 micrograms per liter. While the threshold for arsenic in water defined 10 micrograms per liter by the World Health Organization (WHO). So an average of arsenic in ground water is higher than limits of international standard. The spatial correlation analysis showed that the concentrations of arsenic in groundwater have no strong spatial dependency. So, for zoning this variable, between the nonparametric methods, radial basis function (RBF) by Multiquadric model was used. This method had lowest MAE and MBE index for arsenic in groundwater. The highest concentration of arsenic was in the industrial zone in the north of Hamadan (Hamedan, Tehran road). In general Excessive concentrations of arsenic are visible in the three areas : The first area is between Hamedan and Tehran Road Industrial Estate, that the high rate of abnormalities was found in this area (79.5 μg/L). Also the suburbs of Saleh-Abad and the Bahar city has high arsenic concentration. In these areas, groundwater levels were high and pollutants can penetrate more easily. The results of the contamination map using an indicator kriging method showed that 21.18% of aquifer moderately contaminated and about 10.9% of the aquifer area have a high contamination possibility. Polluted groundwater is matched with agricultural land especially the potato fields.
Conclusion: The results showed that the average concentration of arsenic in groundwater of Hamedan-Bahar basin is more than WHO and Iran department of environmental guidelines. The highest concentration of arsenic in agricultural lands and consequently in groundwater resources is due to the existence of polluting industries, the geological structure of the area where arsenic concentration naturally is high, cultivation of potatoes and other crops in the region and indiscriminate use of pesticides and chemical fertilizers in agriculture.
