Sustainability of water use in irrigated agriculture under future climate scenarios : a case study of Citarum River Basin in Indonesia | |
| Author | Santikayasa, I Putu |
| Call Number | AIT Diss. no.WM-15-01 |
| Subject(s) | Water use--Indonesia--Citarum River Basin Water in agriculture--Indonesia--Citarum River Basin |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Water Engineering and Management, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. WM-15-01 |
| Abstract | Climate change may affect both, short term and long-term water availability and variability, which will, in turn, affect water supply for the irrigated agriculture and thus may cause changes in agricultural productivity. This research assesses the impact of climate change on water availability for irrigated agriculture and evaluates the sustainability of water use under different irrigation management scenarios and the possible responses of farmers in cases when they have to adapt to the changing climatic and socio-economic situation in Citarum River Basin in Indonesia. The specific objectives of this research are: (1) to assess the impact of climate change on future temperature and precipitation; (2) to assess water availability in the future for agriculture under changing climate and socio-economic conditions; (3) to evaluate water use sustainability under future climate and irrigation management scenarios; and, (4) to evaluate the impact of climate change on farmers’ decisions on how to manage irrigation water. The analysis focuses on three future periods: a near-future period from 2011 to 2040 (2020s), a mid-future period from 2041 to 2070 (2050s), and a far-future period from 2071 to 2099 (2080s). A Global Circulation Model (GCM), statistical downscaling, and a hydrological and economic model were employed to achieve the objectives of this research. The hydrological processes were simulated by the Water Evaluation and Planning (WEAP) model using the temperature and precipitation outputs from the Statistical Downscaling Model (SDSM). The WEAP model was calibrated and then applied to assess the availability of water for agriculture for current and future periods. The assessment of sustainability was based on water use performance indicators, namely reliability (Cr), resilience (Cs) and vulnerability (Cv). These indicators were integrated to calculate the sustainability index (SI) under five possible irrigation management scenarios in the future: (1) no change in the area under irrigation and crop intensity (baseline Scenario, S0); (2) an increase in the irrigated area (Scenario, S1); (3) an increase in crop intensity (Scenario, S2); (4) a change in the cropping pattern (Scenario, S3); and, (5) a combination of increased area under irrigation and increased crop intensity (Scenario, S4). The farmers’ responses on managing irrigation, given the changes in water availability in the future, were also evaluated. An integrated biophysical and economic model was applied. Certainty Equivalent (CE), while taking into account future changes in climate, water availability and potential economic conditions. Five cases of water and crop prices were analyzed: (1) without any changes in crop and water prices from the current price level of $0.3/kg and $0/m3 respectively (baseline Case, P0); (2) the crop price stays steady at $0.3/kg but the price of water increases to $0.005/m3 (Case, P1); (3) the crop price stays steady at $0.3/kg but water price increases to $0.033/m3 (Case, P2); (4) the crop price increases to $0.45/kg and the water price increases to $0.005/m3 (Case, P3), and (4) the crop price increases to $0.45/kg and the water price increases to $0.033/m3 (Case, P4).The SDSM showed good performance in downscaling temperature and precipitation. The WEAP model simulated stream flow well with the observed stream flow indicating satisfactory performance of the model. Climate projections indicate that annual average temperature and precipitation are expected to increase compared to the historical period, under both A2 and B2 emission scenarios. The water availability in the future is expected to increase. However, the requirement of water for domestic and industrial sectors is also estimated to increase because of the increase in population, industrial activities and increased economic income. This increase will cause a decrease in the amount of water which can be diverted to the agriculture sector in the future. The Sustainability Index, the collation of the performance indicators, was used to evaluate the various scenarios of irrigation water use in the future under climate change conditions. The study also evaluated future climate, water supply, and irrigation water requirements to assess future sustainability in the study area. It was found that irrigation water requirement will in future, except in the case of the climate only (S0) and changing the crop pattern (S3) scenario. In the S0 scenario, increased evapotranspiration in the future is less than the increase in precipitation. Therefore, the crop water requirement is fulfilled by effective precipitation. In the S3 scenario, the irrigation water requirement decreases by about 35 – 588 million m3, relative to the climate-only (S0) scenario. On the other hand, relative to the S0 scenario, the irrigation water requirement will increase by about 170 – 640, 269 – 643, and 908 – 1373 million m3 when there is an increase in the irrigation area, cropping intensity, and a combination of increased irrigation area and cropping intensity respectively. Considering climate change by itself, and in a combination with the various scenarios, it was found that there is a decrease in reliability, resilience, and vulnerability, as well as in sustainability of water use for irrigation. Even without any changes in the irrigation area and crop, the amount of shortage likely to occur in irrigation water supply in the future will increase because less water will be allocated for irrigation, given the simultaneously increasing demands from domestic and industrial users. Therefore, in combining climate change with the different scenarios, it was found that the performance indicators as well as sustainability index of irrigation water uses decrease in the future. On the whole, the performance indicators will change insignificantly in the future, relative to the climate-only (S0) scenario. On the climate-only (S0) scenario, under the A2 climate projection, the performance indicators and sustainability index in the 2020s and 2050s period will be close to the values obtained under the B2 climate projection. The performance indicators and sustainability index will be lower under B2 than under A2 by the end of the century. However, resilience will decrease by about 50% in the 2020s period when climate change is combined with the increase in crop intensity. Moreover, climate change, combined with the change in the crop pattern scenario, is more adaptive to the B2 climate projection, in which there is a decrease in irrigation water shortage. At the same time, the scenario where there is a change in the crop pattern might experience an increase in the sustainability index of irrigation water use. However, the limitation specific to the crop pattern scenario is that the main food demand by most of the population of the region is rice. Shifting to other crops needs to be evaluated in a future study. Our findings indicate that water availability for agriculture will decrease in the future periods. To sustain the use of water for irrigation in the future, and at the same time, to increase rice production, a strategic plan for increasing the area under irrigation will be essential for successful agricultural adaptation to climate change and this adaptation strategy must be considered as top priority. Changing the cropping pattern might be another option to sustain future agriculture water uses. On the other hand, reduced water availability for agriculture and increased requirement of the same under future climate will affect farmers’ decisions on how to manage irrigation water supplied to them. The results showed that with respect to the availability of water for agriculture in the future, at the farm level, the irrigation water is expected to decrease as per the farmers’ adaptation strategies to future changes. However, it was found that the farmers’ is expected to use all of the available area in the future. The certainty equivalent is expected to change considering the water availability and irrigation water allocation. Strategies regarding the use of water and crop prices that will help in sustaining irrigation water use should consider as the option for the future water management. It may be a valid argument that increasing the water price will reduce future water uses, this study found that the irrigation is expected to decrease up to 30% when the water price increases by about 7%. Therefore, reducing the subsidy by increasing the water price for irrigation was found one of the efficient strategies for future adaptations with respect to the use of water for agriculture. Increasing crop prices is not effective to reduce the water uses for irrigation in the future because the farmers’ are expected to use the maximum water available for irrigation to maximize the crop production. However, increasing crop prices will increase the farmers’ certainty equivalent significantly in the future. A number of key issues have been addressed in this study. In terms of irrigation water uses, performance criteria as the indicators of sustainability, and their selection, are critical issues to keep in mind when applying the sustainability indices to evaluate a scenario. The integration of a biophysical and an economic model was able to cover not only the physical impact of future climatic conditions on the agriculture sector, but also on farmers’ decisions on how to use water under the future climatic conditions. As it was found that the farmers have differing means to cope with these changes, this study suggests that a thorough assessment of farmer behavior, as part of the agriculture management strategy, to sustain the agriculture system in the future is very important. Using the performance criteria combined with the economic assessment of the region in the future, would be the next challenge for future research if an application has to be selected to adapt water management to future developments. Moreover, a comprehensive assessment of the cost and benefit of any possible irrigation management in the future is required to develop an adequate policy framework. |
| Year | 2015 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. WM-15-01 |
| Type | Dissertation |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Water Engineering and Management (WM) |
| Chairperson(s) | Babel, Mukand S. ;Shrestha, Sangam (Co-Chairperson); |
| Examination Committee(s) | Jourdain, Damien ;Sutat Weesakul ;Clemente, Roberto S.; |
| Scholarship Donor(s) | Netherland Scholarship ;Asian Institute of Technology Fellowship; |
| Degree | Thesis (Ph. D.) - Asian Institute of Technology, 2015 |