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Lund University (2014)

Floodwater harvesting for artificial recharge of groundwater - estimation and prediction for arid Iran

Hashemi, Hossein

Titre : Floodwater harvesting for artificial recharge of groundwater - estimation and prediction for arid Iran

Auteur : Hashemi, Hossein

Université de soutenance : Lund University

Grade : Dissertation (2014)

Résumé
Groundwater depletion in arid and semiarid areas is of increasing concern. Increasing water demand due to increasing population and climate change impacts have intensified the water shortage problems and put further stress especially on groundwater. Water harvesting techniques have been traditional solutions to water scarcity problems in the arid and semiarid Middle East for thousands of years. These techniques are increasingly being encouraged and at present there has been a renewed interest to find improved methods for water harvesting and artificial recharge in many arid countries. In order to understand the function and efficiency of an introduced floodwater harvesting system, the contribution of the system for total recharge and crop yield needs to be quantified using proper techniques and experiments. This dissertation presents a combination of modeling techniques and field experiments to quantitatively evaluate a system for flash flood harvesting in arid southern Iran. To investigate the performance and hydrological function of an improved floodwater spreading system, a groundwater model together with water balance approach were developed to estimate the magnitude of recharged water through both natural riverbed and artificial recharge system. Also, effects of pumping rates on the reservoir from 1993 through 2007 were assessed. The impacts of future climate scenarios on surface and groundwater resources were also simulated using a sequential modeling approach. Further, as the floodwater spreading system is a multi-functional and multi-purposed system, the contribution of the system in spate irrigation farming was tested through a three-year field experiment. In the groundwater modeling, the recharge rate and aquifer hydraulic parameters were estimated through inverse modeling approach. The model was calibrated and verified based on the observed hydraulic head in observation wells and model precision, uncertainty, and model sensitivity were analyzed in all modeling steps. The results showed that in the steady-state groundwater flow with no recharge from surface water, the studied aquifer is mainly recharged by a fault, which conducts water into the area from an upper sub-basin. Estimation showed that the recharge amount in the studied floodwater spreading system varied from a few hundred thousand cubic meters per month during drought periods to about 4.5 million cubic meter per month during rainy periods. The results also showed that in a normal year without extreme events the floodwater spreading system is the main contributor to recharge with 80% and the ephemeral river channel with 20% of total recharge in the studied area. The climate change impact scenarios revealed that the abstraction has the most substantial effect on the groundwater level and the continuation of current pumping rate would lead to a groundwater decline by 18 m up to 2050. The field cultivation of barley crop inside and outside the floodwater spreading system displayed a significant increase in yield for the plots inside the system relative to the plot outside the system. As a summary, recognizing that groundwater depletion is occurring in many arid areas due to the over-exploitation as a consequence of population growth and climate change, multi-purpose floodwater harvesting for artificial recharge and spate irrigation could be a parsimonious and appropriate way to efficiently utilize the potential agricultural capacity of the arid environments. In the floodwater spreading system, a flash flood can be harvested and stored beneath the ground to be abstracted for irrigated agriculture during the dry season while the crop can be directly irrigated by floods in the wet season. Therefore, the groundwater abstraction can be minimized, particularly, during the wet season and water can be saved for the dry season

Mots clés : Artificial recharge, Groundwater modeling, Climate change, Spate irrigation, Arid area, FWS, GBP

Présentation

Page publiée le 5 juillet 2014, mise à jour le 11 mars 2019