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University of Kassel (2018)

Hydro-economic Modeling for Optimization of Sustainable Water Management of a River Basin in the Wake of Climate Change : Case Study of the Zarrine River Basin (ZRB), Iran

Emami, Farzad

Titre : Hydro-economic Modeling for Optimization of Sustainable Water Management of a River Basin in the Wake of Climate Change : Case Study of the Zarrine River Basin (ZRB), Iran

Auteur : Emami, Farzad

Université de soutenance : University of Kassel

Grade : Doktor der Ingenieurwissenschaften (Dr.-Ing.) 2018

Résumé partiel
Food and water security will be a great future challenge due to the growth of population and unsustainable water usage. The renewable water resources in the MENA region including Iran, are expected to decline. This situation is exacerbated by the increasing demands and the rising climate variability in the wake of global climate change affecting adversely the available water resources. This thesis research attempts to evaluate the impacts of climate change and water demands on the hydrological and environmental characteristics of the Zarrine River Basin (ZRB), the headwater of Lake Urmia of Iran, which has been desiccating in recent years, being so on the brink of an environmental disaster, together with the Boukan Dam operation and then recommends some adaptation strategies, in order to balance properly the future water resources and demands in the ZRB. This thesis is divided in 6 chapters structured as 5 individual papers with the following contents : 1- In the first Chapter a general introduction of the thesis is given and the research area and study objectives are described. 2- In Chapter 2 the ZRB’s water resources response to the impacts of a changing climate, with emphasis on Boukan dam’s future inflow, are simulated up to year 2029 by means of the basin-wide hydrologic model SWAT. The future projections of precipitation and temperature extracted from MPI-ESM-LR-GCM (RCP 2.6 and 4.5) and HADCM3-GCM (SRES A2 and B2) output, respectively, are downscaled using Quantile Mapping (QM) bias-correction and SDSM, respectively. From two variants of QM employed, the Empirical-CDF-QM model decreases the biases of the raw GCM- precipitation the most. The SWAT- model is then calibrated and validated with historical (1981-2011) ZR-streamflow, using the SWAT-CUP- automatic program. The subsequent SWAT-simulations for the future 2012-2029 period indicate a reduction of the inflow to Boukan Dam as well as of the overall water yield of ZRB for all SRES/RPC- scenarios. In summary, based on these predictions and the expected increase of water demands, the ZRB is likely to face a water shortage in the future, with a water yield decrease between -23% and -36%, unless some adaptation plans are implemented for a better management of the water resources in the region. 3- Modeling the hydrologic responses to future changes of climate is important for improving adaptive water management. In Chapter 3 the impacts of future climate change signals on various hydro-climatic variables in the ZRB are assessed. To that avail, two SD-methods, SDSM and ECDF non-stationary Quantile Mapping (QM), are used to downscale the climate variables of min. and max. temperatures and precipitation for the near (2020-2038), middle (2050 to 2068) and far (2080 to 2098) future periods for three RCP emission scenarios. The performances of the downscaling methods are compared to each other for a past “future” period (2006-2016), and the QM is found to be better and is so selected in the subsequent SWAT- Zarrine-streamflow simulations, with the model calibrated and validated for the reference period (1991-2012). The impacts of climate change on the hydrologic response of the river basin, specifically, the inflow to the Boukan reservoir, the reservoir dependable water (DWR) supply are then compared for three RCPs in the three future periods, assuming (1) the “current” consumptive demand to be continued in the future and (2) a more conservative “recommended” one. A systematic future shortage of the available water is obtained for case (1) which can be mitigated somewhat for (2). Finally, the SWAT- predicted ZRB outflow is compared with the Montana-based estimated environmental flow of the ZR. The latter can successfully be sustained at good and fair levels for the near and middle future periods, but not so for the summer months of the far future period, particularly, for RCP85. 4- The operating policies of a reservoir dam depend on the upstream river’s inflow. As the latter may be affected by impacts of climate change which, in turn, may alter the water supply, studies to this regard are of utmost importance to ensure the sustainable development of the future water resources in the area. In Chapter 4, firstly the calibrated rainfall-runoff model SWAT is used to predict the various hydrological components of the ZRB for the historical and future periods until 2049, using downscaled input precipitation and temperatures of three RCP-scenarios captured from one of the projections of the CMIP5-GCM ensemble, the CESM1-CAM5-model. The streamflow scenarios are then employed in the MODSIM water management model to simulate the present-day and future water resources of the basin and to determine the optimal operation of the Boukan Dam, based on some prioritization of the water allocation. Finally, the impacts of climate and demand changes on the dam operation are evaluated by comparing future and historical MODSIM- simulated average water budget and supply/demand ratio (SDR) for the three CESM-model scenarios which show that the region will face more intensive water shortages.

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