Irrigation
H. Sarvi Sadrabad; A. Zare Chahouki
Abstract
Introduction: Inter-basin water transfer affects the environment, culture and economy of donor and recipient basin. In this regard, one of the most important aspects are the positive and negative effects on the quality of groundwater in the recipient basin. Spatio-temporal changes of groundwater ...
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Introduction: Inter-basin water transfer affects the environment, culture and economy of donor and recipient basin. In this regard, one of the most important aspects are the positive and negative effects on the quality of groundwater in the recipient basin. Spatio-temporal changes of groundwater quality as the results of inter-basin water transfer, plays an important role in water resources management. Thus, this study attempts to investigate the temporal trends of groundwater quality parameters using Mann-Kendall test and Sen's slope estimator. In addition, spatial changes of groundwater quality and the effects of inter-basin water transfer were studied.Materials and Methods: In this study, non-parametric methods and interpolation models were used to evaluate the spatio-temporal patterns of groundwater quality parameters in the Yazd-Ardakan plain. Mann-Kendall nonparametric test and Sen's slope were used to examine the temporal trends in the span of 2000 to 2020. The interpolation models and groundwater quality index (GQI) were used to study the spatial patterns and classify the quality of groundwater. The assessment of quality parameters of all studied wells including Ca2+, Mg2+, Cl-, Na+, SO42- and TDS were studied in equal time periods. Groundwater quality measurements were performed twice a year using a volumetric method, one in spring and the other one in autumn. The World Health Organization (WHO) standard was considered to compare values of different parameters in the plain.Results and Discussion: A decreasing trend was observed in SO42-, Na+ and TDS parameters in most wells and there was an increasing trend for Ca2+, Mg2+ and Cl- parameters. Considering WHO classification standard, all the studied parameters were in the allowable ranges except TDS. The parameter ranking showed that TDS, Cl- and Mg2+ had the greatest impact on the quality of aquifer groundwater. The Mg and TDS parameters had the highest and the lowest changes, respectively during 2000 to 2020. Results of the GQI showed that the total quality of the Yazd-Ardakan aquifer was in the moderate class and acceptable because of relatively large decrease in the groundwater in the span of the studied period. However, the decrease in groundwater quality was negligible. Changes of the quality map showed that the most negative quality changes were related to the Yazd, Taft, Meybod, Ardakan and northern regions (Chah-Afzal desert). This indicates high groundwater pumping in these areas and being located near the desert area. The most positive quality changes belonged to the central and southern part of the aquifer.Conclusion: Comparison of the interpolation models showed that the geostatistical methods can show better results than the definitive methods in zoning groundwater quality parameters. The Kriging and IDW models were the best models and consistent with the results of the research. The quality of groundwater was acceptable, while the reduction in quality was very low and negligible in the Yazd-Ardakan aquifer during the studied period. The temporal trends of SO42-, Na+ and TDS had either a negative significant trend or no trend in the Yazd area. Considering ranking maps, TDS, Cl- and Mg2+ had high impacts on determining the GQI. These trends were positive in Yazd city and consequently the GQI maps could not confirm the negative temporal trend and zoning maps. This finding showed that the use of qualitative indicators could neutralize the effects of the parameters on each other and provide a better and acceptable result. In all, the transfer water with appropriate quality could control the increase of the TDS, SO42-, Na and caused an increase in Cl- in these areas. There are many effective factors to study water quality, so its description seems to be difficult. Therefore, using water quality indicators can provide total water quality conditions in a concise and understandable way.
Irrigation
F. Hayatgheibi; N. Shahnoushi; B. Ghahreman; H. Samadi; M. Ghorbani; Mahmood Sabouhi
Abstract
Introduction: The development of water resources in many cases has led to increased economic welfare, improved living and health standards, food production, etc. However, in some cases due to the insufficient attention to all aspects of these projects, the irreparable environmental effects and subsequent ...
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Introduction: The development of water resources in many cases has led to increased economic welfare, improved living and health standards, food production, etc. However, in some cases due to the insufficient attention to all aspects of these projects, the irreparable environmental effects and subsequent social and economic effects have been imposed on society. Paying attention to environmental water requirements is one of the most important issues in decision making in water resources development plans. The objective of this study is to assess river environmental water requirements in upstream and downstream of Beheshtabad Dam. Beheshtabad Dam has designed to build on the Karun River for water transfer from Karun to Zayanderood basin. But it has not been implemented due to the various problems and challenges. Materials and Methods: Protecting and restoring river flow regimes and hence, the ecosystems they support by providing environmental flows has become a major aspect of river basin management. Environmental flows describe the quantity, timing, and quality of water flows required to sustain freshwater,estuarine ecosystems,the human livelihoods, and well-being that depend on these ecosystems. Over 200 approaches for determining environmental flows now exist and used or proposed for use in more than 50 countries worldwide. In the present study, hydrological methods have been used. These methodes include Tennant and modified Tennant, Flow Duration Curve (FDC) and FDC shifting (for different environmental management classes). For this purpose, four hydrometric stations (three stations upstream and one station downstream of the dam) have been selected. Results and Discussion: The results of the study showed that the river water flow had not been sufficient to meet environmental water requirements in several cases, especially in years when the region was experiencing mild to moderate drought conditions. According to the Tennant method, the minimum environmental flow requirement averages based on Beheshtabad, DezakAbad, Kaj, and Armand stations data were 3.80, 5.06, 6.99, 22.01 m3/s, respectively. Using the mentioned stations data, , the minimum environmental flow requirement averages were 3.62, 6.07, 7.91, 23.67 m3/s based on the modified Tennant method. According to the flow duration curve method, minimum environmental flow requirements (Q95) were 1.96, 5.1, 8.32, 30.62 m3/s, using data collected from Beheshtabad, DezakAbad, Kaj, and Armand stations, respectively. The results of the flow duration curve shifting method indicated that the river water flow did not meet the river environmental water requirements in different environmental management classes in some months and years. Comparative results of different methods revealed that the minimum environmental flow requirement of Beheshtabad River upstream of Beheshtabad Dam was 1.22-16.75 m3/s from September to April (based on FDC shifting method, class C). The estimated minimum environmental flow for Koohrang River was 3.69-16.81 m3/s from September to April. The downstream of the dam, Karun River requires a minimum flow rate of 20.8-73.29 m3/s from September and October to April (based on FDC shifting method, class E). Conclusion: According to the results of various methods used in this study, the Karun River flow is not enough to meet the minimum river environmental water requirements in some years and months. Therefore, decision-makers must pay attention to the environmental water requirements in decisions related to the development plans and water transfer from this river. It should be noted that the river environmental water requirements have not been met completely when the region has experienced moderate or mild drought, which would be more acute in cases of more severe drought conditions. Therefore, the current surplus water of this basin may not be a sustainable source to transfer to another basin.
