This study assessed flood inundation of the Ciliwung River Basin, Greater Jakarta to improve the urban water environment under climate change and unplanned urbanisation. The 1‐day maximum precipitation data for 50‐ and 100‐year return period under current and future climate conditions were used to assess the impact of climate change. Precipitation output of the MRI‐CGCM3, MIROC5, and HadGEM2‐ES General Circulation Models (GCMs) with RCP 4.5 and 8.5 emission scenario over periods 1985–2004 and 2020–2039 representing current and future climate conditions, respectively, were used. Similarly, land use data of 2009 and 2030 were used to represent the current and future conditions, respectively. The HEC‐HMS model was used to simulate the river discharge at Katulampa, which represents the outlet location for the hydrologic modelling and the inlet location for the flood inundation modelling. FLO‐2D, a two‐dimensional hydrodynamic model, was used to simulate current and future flood inundation simulations. Increasing flood inundation areas and depths (6% to 31% for different GCMs) in the future reveal the need to improve flood management tools for the sustainable development of urban water environments.
Abstract:The hydrological conditions upstream of the Ciliwung watershed are changing due to climate and land-use changes. Any changes in this area may increase the flood frequencies which may have countless consequences downstream of the watershed where the Jakarta city is located. We simulated the effects of land-use and climate changes on flooding (e.g., peak flow and river discharge) in the upper Ciliwung River basin in Greater Jakarta, Indonesia. Hydrologic Modeling System (HEC-HMS), a rainfall-runoff simulation model, was used to simulate peak river discharge values for current and future conditions. The model was calibrated and validated based on the observed river discharge data from February 2007 and January 1996, respectively. The statistical analysis showed that the performance of the model is satisfactory, with Nash-Sutcliffe efficiency 0.64 and 0.58 for calibration and validation, respectively. The coefficients of determination values are 0.86 and 0.82, respectively. The effect of the projected land-use changes alone in 2030 increased the peak flow by approximately 20%. When considering the land-use changes in conjunction with the future climate scenario, the peak flow based on the precipitation corresponding to a 50-year return period in 2030 increased by 130%. Based on the results of this study, it is urgent that a flood management plan be implemented in the target area to reduce flooding in the near future.
The semi-arid regions of Iran have experienced severe water resources stress due to natural (e.g., drought) and anthropogenic (e.g., depletion of water in various sectors) factors. Assessing the impact of climate change on water resources and crop production could significantly help toward better water management and hence prevention of land degradation in this area. A hydrological model of the Razan–Ghahavand basin was used as a representative case study of a semi-arid region of Iran. Future climate scenarios in the mid-21st century were generated from four global circulation models (GCMs) with three scenarios under the fourth assessment report of Intergovernmental Panel on Climate Change emission projections. The GCMs have been downscaled based on observed data at 10 climate stations across the basin. The results showed that for the basin as a whole, the mean annual precipitation is likely to decrease while the maximum temperature increases. The changes in these two climate variables resulted in substantial reduction in groundwater recharge as the main source of water supply in this area. Furthermore, soil water content was decreased which resulted in the reduction of crop yield in rain-fed areas. Indeed, the risk of drought in the south and flooding in the north was high.
Abstract:The A-Luoi district in Thua Thien Hue province of Vietnam is under extreme pressure from natural and anthropogenic factors. The area is ungauged and suffering from data scarcity. To evaluate the water resources availability and water management, we used Soil and Water Assessment Tools (SWAT). A multi-approach technique was used to calibrate the hydrological model. The model was calibrated in three time scales: daily, monthly and yearly by river discharge, actual evapotranspiration (ETa) and crop yield, respectively. The model was calibrated with Nash-Sutcliffe and R 2 coefficients greater than 0.7, in daily and monthly scales, respectively. In the yearly scale, the crop yield inside the model was calibrated and validated with Root Mean Square Error (RMSE) less than 2.4 ton/ha. The water resource components were mapped temporally and spatially. The outcomes showed that the highest mean monthly surface runoff, 323 to 369 mm, between September and November, resulted in extreme soil erosion and sedimentation. The monthly average of actual evapotranspiration was the highest in May and lowest in December. Furthermore, installing "Best Management Practices" (BMPs) reduced surface runoff in agricultural lands. However, using event-based hydrological and hydraulic models in the prediction and simulation of flooding events is recommended in further studies.
Abstract:Modeling insecurity under future climate change and socio-economic development is indispensable for adaptive planning and sustainable management of water resources. This case study strives to assess the water quality and quantity status for both the present and the near future in the Ciliwung River basin inside the Jakarta Province under different scenarios using population growth with planned additional wastewater management infrastructure by 2030 as mentioned in the local master plan, and comparing the above conditions with the addition of the effects of climate change. Biochemical oxygen demand (BOD), chemical oxygen demand (COD) and nitrate (NO 3 ), the three important indicators of aquatic ecosystem health, were simulated to assess river pollution. Simulation results suggest that water quality in year 2030 will further deteriorate compared to the base year 2000 due to population growth and climate change, even considering the planned wastewater management infrastructure. The magnitude of impact from population growth is far greater than that from climate change. Simulated values of NO 3 , BOD and COD ranged from 6.07 to 13.34 mg/L, 7.65 to 11.41 mg/L, and 20.16 to 51.01 mg/L, respectively. Almost all of the water quality parameters exceeded the safe limit suitable for a healthy aquatic system, especially for the year 2030. The situation of water quality is worse for the downstream sampling location because of the cumulative effect of transport of untreated pollutants coming from upstream, as well as local dumping. This result will be useful for local policy makers and stakeholders involved in the water sector to formulate strategic and adaptive policies and plan for the future. One of the potential policy interventions is to implement a national integrated sewerage and septage management program on a priority basis, considering various factors like population density and growth, and global changes for both short-and long-term measures.
Abstract. Hydrological modeling of ungauged basins which have a high risk of natural hazards (e.g., flooding, droughts) is always imperative for policymakers and stakeholders. The Aluoi district in Hue province is a representative case study in Central Vietnam, as it is under extreme pressure of natural and anthropogenic factors. Flooding, soil erosion and sedimentation are the main hazards in this area, which threaten socio-economic activities not only in this district but also those of the area downstream. To evaluate the water resources and risk of natural hazards, we used Soil and Water Assessment Tools (SWAT) to set up a hydrological model in the ungauged basin of Aluoi district. A regionalization approach was used to predict the river discharge at the outlet of the basin. The model was calibrated in three time scales: daily, monthly and yearly by river discharge, actual evapotranspiration (ETa) and crop yield, respectively. The model was calibrated with Nash-Sutcliff and an R2 coefficients greater than 0.7, in daily and monthly scales, respectively. In the yearly scale, the crop yield inside the model was calibrated and validated with RMSE less than 2.4 ton/ha, which showed the high performance of the model. The water resource components were mapped temporally and spatially. The outcomes showed that the highest mean monthly surface runoff, 700 to 765 mm, between September and November, resulted in extreme soil erosion and sedimentation. The monthly average of actual evapotranspiration was the highest in May and lowest in December. Furthermore, installing "Best Management Practice" (BMPs) reduced surface runoff and soil erosion in agricultural lands. However, using event-based hydrological and hydraulically models in the prediction and simulation of flooding events is recommended in further studies.
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