Assessing the hydrological situation of Talau watershed, Belu regency, East Nusa Tenggara

This report presents results of a ‘rapid apprai sal’ of the hydrological situation in Talau Watershed, Belu District in East Nusa Tenggara (Indonesia). The main objective of this study was to assess the hydrological situation of Talau wa tershed, to provide information on what and where the payment for watershed services could be focused. Talau also has a very dry climate, with aver age annual precipitation of around 1600 mm/year. Around 95% of the rainfall falls within 4 months of rainy season, causing the rest of the year in a dry condition. Due to this condition, the dominant land cover classes in Talau watershed are grassland. Water springs are the main source of water for peopl e in the area. The main focus of this study is in Lahurus, where the water spring is curre ntly used by the local people for household consumption and agricultural irrigation, as well as by the public water company (PDAM) for drinking water in another watershed. Local knowledge surveys to local community and policy makers as stakeholders in Talau watershed revealed that their main hydrological concerns are: 1. Sensitivity to climate variability and im balance of demand and supply of water in dry periods, which leads to: a. Concerns over low flows and water shortage in dry season, shortfalls at intake of drinking water supply; b. Lack of landscape scale water storage, w ith ‘overflow’ conditions in the second part of the rainy season, and shor tfalls in the dry season 2. Soil erosion that could add further degradation to the landscape Both local community and policy makers of Ta lau believe that good land management could improve soil conditions and it is im portant to reduce further degradation of the watershed. They suggested that activities such as planting trees and developing infiltration pits could help in reducing the hydrological problems they are facing. From the limited information available on river fl ow, the overall pattern of Talau river flow can be described in three phases: the early part of the rainy season when the soil and landscape storage capacity for water is recharged, the second part of the rainy season when a larger proportion of the current rainfall is transmitted to the river, and the dry season when river (and spring) flow depends on the gradual release of stor ed water. Our analysis of hydrological data confirms with our assessment on Talau watershe d function (using modeling approach), where we explored how the year-to-year variation in ra infall translates to variations in hydrological behaviour. The buffering capacity of the Talau wa tershed is less in years with high rainfall and consequently high total water discharge. A si milar situation occurred for ground water discharge. River flow in the Talau watershed is strongly seasonal; the risks of flash floods is - iii - especially high in the second part of the rai ny season when the storage capacity of the landscape is saturated and strong rainfall is passed on to the river without much buffering.

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DOI:

https://doi.org/10.5716/WP15431.PDF

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