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Planning for Groundwater Sustainable Management Case Study: Nishapur Plain

Khakbazan Fard, Faezeh | 2020

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53237 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Abrishamchi, Ahmad
  7. Abstract:
  8. In recent years, an increasing demand of water on one hand and over-exploitation of groundwater resources on the other hand lead to the unsustainability of these resources worldwide. Due to arid and semi-arid climate in Iran, groundwater resources play an essential role in food production, as well as domestic and industrial water supply. Increasing population, scarcity of surface water resources, and effects of worldwide and regional climate change have resulted in over-exploitation of groundwater resources in the country and threatens the water security of the nation. The present study aims to estimate groundwater sustainable yield, examine effects of spatial and temporal scale, water demand supply in the condition of limiting groundwater withdrawal to the groundwater sustainable yield, the effect of uncertainty in the different factors on the water demand supply and propose a plan for groundwater sustainable use in Nishapur Plain, in the north-east of Iran. In this study, groundwater sustainable yield is estimated using concept of Capture. In investigating the effects of spatial scale the area of the plain is divided into several zones, with estimation of groundwater recharge and discharge for each zone. The temporal scale in this investigation, refers to the different time-scales used to estimate the average value of groundwater recharge and discharge. The results of the transient groundwater model of Nishapur Plain, revealed that average annual groundwater storage depletion is about 311 MCM during the 8-year period of 2005-2013 with the minimum, average, and maximum water table decline of 0.6 m, 7.7 m and 11 m, respectively. To achieve these goals, five different scenarios were defined to investigate the effect of the spatial scale on the sustainable yield. Then, the effect of temporal scale was examined in the four different scenarios including 1-year, 6-month, 3-month, and 1-month using the best spatial scale. In each of the scenarios in the present study, the groundwater sustainable yield is determined in a long planning horizon (more than 75 years) and a short planning horizon, which was assumed to be equal to the simulation period (8 years in this study). The study results suggest that sustainable yield is closely correlated to the spatial and temporal scales, and refinement of spatial and temporal scales increases sustainable yield from 39% to 59% of the current pumping volume. This difference in sustainable yield is equal to about 100 MCM of water or about 8000 ha of irrigated land. Also, based on the results, changing the temporal scale does not have a significant effect on the groundwater sustainable yield and it is equal to maximum 5 and 10 MCM in the long and short planning horizon respectively. In the next step, supplying agricultural water demand of major crops in Nishapur Plain is investigated in the condition of limiting groundwater withdrawal to the groundwater sustainable yield in different scenarios. Since in this condition, it is not possible to supply water demands completely, in this study increasing irrigation efficiency and changing crop pattern are considered as the possible strategies for increasing water productivity and coping with the social and economic effects caused by water scarcity. The results show that in the long planning horizon, with increasing irrigation efficiency to 65%, the existing water demands are supplied completely and in the short planning horizon even with increasing irrigation efficiency to 80% it is not possible to supply water for barley and cotton. The results also show that due to the special conditions of the current cropping pattern in Nishapur Plain, it is not possible to make much change in the cropping pattern. Therefore, the proposed cropping pattern, in which half of the harvested sugar beet area in the current condition is allocated to colza, does not have significant effect on the agricultural water demand in the Nishapur Plain. In the last step of the study, the effects of uncertainties in the groundwater withdrawal, cropping pattern, and irrigation efficiency on the supplying agricultural water demands, are investigated using the concepts of conditional probability and Bayes law. According to the results, by increasing the irrigation efficiency to 65%, using the current cropping pattern and limiting groundwater withdrawal to the maximum groundwater sustainable yield, it is possible to supply groundwater demand in the long planning horizon completely in addition to achieving maximum gross income. The results of this study can be extended to other semi-arid agricultural areas, which primarily depend on groundwater
  9. Keywords:
  10. Uncertainty Analysis ; Groundwater Level Prediction ; Bayes Probablity Theorm ; Capture Zone ; Groundwater Sustainable Yield ; Temporal and Spatial Scale ; Nishapur Plain ; Groundwater Modeling

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