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Water deficits in Bogowonto : evaluation of hydrological effects of stakeholder prioritized response options for the agricultural water deficits in Bogowonto, Indonesia

Zwol, G. van (2014) Water deficits in Bogowonto : evaluation of hydrological effects of stakeholder prioritized response options for the agricultural water deficits in Bogowonto, Indonesia.

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Abstract:Indonesia is a tropical country situated in South-East Asia that faces water scarcity during the dry season. The yearly returning agricultural water deficits caused by periods of insufficient rain, lack of water retention capabilities, degraded irrigation infrastructure and inefficient management of the irrigation weirs result in sup-optimal cropping conditions for the farmers who depend on the irrigation water flows. The National Middle Term Development Plan (RPJPN) of the Indonesian government includes options to increase the water availability and reduce the agricultural water demand. However, the RPJPN does not include the opinions of the local stakeholders in the decision process on measures which reduce the water deficits, nor does it include a specific assessment for the present and future hydrological conditions of Bogowonto. The overall objective of this study is to select potential measures for the Bogowonto catchment to decrease the agricultural water deficits by following a participatory approach to obtain preferred measures and by applying a water allocation model which addresses the spatial and temporal variations in the agricultural water deficit. This study includes the construction of a water allocation model with multiple scenarios for climate variability (i), results from participatory meetings for the up-, mid- and downstream irrigation weirs (ii) and statements on stakeholder prioritized measures to assess the agricultural water deficit (iii). Based on this, the historical (1992-2012) and future (2025-2045) agricultural water deficits are simulated and a set of measures is proposed based on the prioritization of the stakeholders and a multi-criteria analysis. These results can be of great value if the government is recipient to include the opinion of local stakeholders in the process of decreasing the agricultural water deficit. Moreover it can provide direction for future catchment plans of Bogowonto. Main findings of this study are:  For the upstream irrigation weir the agricultural water deficit varies around 350 [330-370] mm for the driest simulated year. The brackets show the minimum and maximum value as modeled by the climate scenarios for the driest year. The months May-June and October-November are the largest contributors to the cumulative annual water deficit, as a direct result of the low rainfall in these periods and the high agricultural water demand. For five out of the twenty simulated years the agricultural water deficit exceeds 50 mm/year. In other words, every four years the annual water deficit exceeds 50 mm. This value is significantly lower compared to the mid- and downstream irrigation areas, mainly because the upstream area receives more precipitation.  For the midstream irrigation weir the agricultural water deficit is 750 [620-810] mm for the driest simulated year. The peaks of this cumulative annual water deficit take place during May, June and October. Sixteen out of twenty years have a water deficit which exceeds 50mm per year. To put it differently, almost every year the annual water deficit exceeds 50 mm.  For the downstream irrigation weir the future agricultural water deficit is 650 [750-520] mm per year for the driest simulated year. The peak of the cumulative annual water deficit takes place during October. Thirteen out of the twenty years have a water deficit which exceeds 50mm per year. In other words, every one and a half year the annual water deficit exceeds 50 mm.  The participatory sessions illustrated the rehabilitation of the irrigation infrastructure was preferred out of all simulated measures by all stakeholders, which can be explained by the current degraded status of the irrigation infrastructure in Bogowonto. Secondly the stakeholders from the mid- and downstream irrigation weirs preferred the construction of an upstream reservoir that would satisfy the larger irrigation demand during periods of insufficient rain like May, June and October. Enrolling a new cropping pattern was not preferred by the stakeholders, due to the lack of successful examples at neighboring farms and alternatives like the reservoir and irrigation efficiency were much more popular.  The stakeholders in this study are the farmers at the irrigation weir, the employees of the irrigation weir and the local government. Other measures which were proposed by the stakeholders like small rain fed reservoirs, heightening of river banks to stop the annual floods or stopping illegal extraction by farmers from surface- or groundwater have not been selected for simulation. These measures are outside the scope of this research, or RIBASIM was not able to simulate such a measure or the level of scale was inappropriate. During the final participatory session the local government proposed the combination of the measures ‘irrigation efficiency + reservoir’, since none of the measure was able to reduce the annual water deficit to such an extend it satisfied the stakeholders.  For the upstream irrigation weir the maximum water deficit decreases from 350 [330-370] to 0 mm for the driest simulated year. During none of the 20 simulated years a water deficit is present. This means no water deficits are expected for the future.  For the midstream irrigation weir the maximum water deficit decreases from 750 [620-810] to 250 [220-260] mm considering the driest simulated year. In addition, three out of the twenty annual simulated years still exceed 50 mm per year. To put it in another way, roughly every seven years a water deficit takes place which exceeds the annual water deficit of 50 mm.  For the downstream irrigation weir the maximum water deficit decreases from 650 [750-520] to 90 [80-100] mm for the driest simulated year. It is expected every seven years the annual water deficit still exceeds the 50 mm. These results lead to the following recommendations for the operational management of Bogowonto catchment:  Firstly the measures “irrigation efficiency” and “construction of the reservoir” are able to positively contribute in the reduction of the agricultural water deficit for 2025-2045 and are supported by the majority of the stakeholders which effectuates a positive implementation of these measures.  Secondly is it recommended to perform research on the current quality of the irrigation channels and decide which parts should be replaced to achieve an irrigation efficiency of at least 65% in 2035.  Thirdly if one is considering the construction of the reservoir, it is recommended to perform research to the exact location and dimensions of the reservoir, which should be communicated to the local community in an early stage. In this way added value for the local community can be developed and a win-win scenario is established for the farmers, civilians and government.
Item Type:Essay (Master)
Clients:
General Directorate of Water Resources & Ministry of Public Works (BBWS Serayu Opak), Indonesia
Ministry of Forestry, Indonesia
Department of Water Resources Management Central Java (PSDA Probolo), Indonesia
University Gadjah Mada, Indonesia
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
Link to this item:http://purl.utwente.nl/essays/65865
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