Loes River


The Loes River is the longest river in Timor-Leste with a total length of and one of the few perennial rivers in the country's north.
The river combines with its tributaries to make up Timor-Leste's largest river system, and its catchment or drainage basin extends into the province of East Nusa Tenggara in Indonesia.
The river and tributaries drain from the central mountains of Timor in a generally northeasterly direction into Ombai Strait. However, the river itself flows in a northwesterly direction, along the border between Bobonaro and Liquiçá municipalities in Timor-Leste.

Course

The river is fed by a large number of gullies, creeks, streams and other rivers. Its headwaters are mainly in the portion of Timor's central mountains ranging between, on the one hand, Belu Regency, Indonesia, and Cova Lima municipality, Timor-Leste, both southwest of the river's mouth, and, on the other hand, Liquiçá municipality, Timor-Leste, to the mouth's east.
From the southwestern headwaters, the river's southwestern and southern tributaries flow for the most part in a northeasterly direction through, or along the borders of, Belu Regency, Indonesia, and Bobonaro municipality, Timor-Leste, to the source of the river, at the confluence of the and rivers. That confluence is on the border between Bobonaro and Liquiçá municipalities, a short distance upstream of the tripoint between those two municipalities and Ermera municipality, Timor-Leste.
At the river's source confluence and at the tripoint, the waters of its southwestern and southern tributaries converge with the waters from its southeastern and eastern tributaries. The river then flows, generally in a northwesterly direction, along the border between Bobonaro and Liquiçá, until it discharges into Ombai Strait, at the western end of the border between Suco, Atabae administrative post, Bobonaro, and Suco, Maubara administrative post, Liquiçá.
The river is one of the few perennial streams in the north of Timor-Leste, one of only three such northern watercourses that can potentially be inhabited by saltwater crocodiles all year round. Its main channel, formed by the Marobo and Nunura Rivers, is braided, varies in width from about up to, and is wider in its lower reaches.
At the mouth of the river, Ombai Strait is part of the Banda Sea, which extends a little further west, to longitude 125° East; beyond that meridian, the strait is part of the Savu Sea. A short distance upstream of the river mouth is the Loes Bridge, which was opened in 1991 and is the main bridge connecting West Timor, Indonesia, and Bobonaro with Dili, the national capital of Timor-Leste.
In order of entrance, the river's main tributaries include the following:
  • Merak River: rises in Fatumean administrative post in the far north west of Cova Lima municipality; flows northwest into, and then northwards through, Belu Regency, to enter the Talau River on the border between Belu Regency and Suco, Bobonaro municipality;
  • Talau River : rises at Atambua, Belu Regency, near the westernmost point of the border between Belu Regency and Bobonaro municipality, flows southeast, and then northeast, forming the border between those two territories, until it merges with the Malibacu River to form the Nunutura River ;
  • Malibacu River : rises in Suco in south central Bobonaro municipality; flows northwest to the border between that municipality and Belu Regency, and then further northwest, forming the border between those two territories, until it merges with the Talau River to form the Nunutura River ;
  • Nunutura River : flows from the confluence of the Talau and Malibacu Rivers northeast through Bobonaro municipality to the border between Bobonaro and Liquiçá municipalities, very close to the tripoint between those two municipalities and Ermera municipality, where it merges with the Marobo River to form the Loes River;
  • Bulobo River: rises near Maliana in south central Bobonaro; flows generally northwards until it enters the Nunutura River in central Bobonaro municipality;
  • Marobo River: rises in Bobonaro municipality, near the southern point of the border between Bobonaro and Ermera municipalities; flows northwest, for the most part forming the border between those two municipalities, to the border between Bobonaro and Liquiçá municipalities a short distance southeast of the tripoint between those two municipalities and Ermera municipality, where it merges with the Nunutura River to form the Loes River;
  • Gleno River : rises near Gleno in northeastern Ermera municipality, where it is fed in part by water draining from ; flows generally westwards, largely along the border between Ermera and Liquiçá municipalities, until it enters the Loes River at the tripoint between Bobonaro, Ermera and Liquiçá municipalities, a short distance northwest of the latter's source.

    History

For the period 1953 to 1979, which included the final years of the Portuguese colonial era in Timor-Leste, the colonial administration's Plans of Development identified the river as one of the locations targeted for the boosting of agricultural development. The III Plan of Development, for the years 1968 to 1973, placed particular importance on that objective.
In 1979, during the Indonesian occupation of East Timor that had begun in 1975, the Indonesian army took over the Liquiçá area, and certain reconstruction work was commenced there.
Two years later, Catholic Relief Services and the United States Agency for International Development established the East Timor Agricultural Development Project, which was later transferred to Timorese control, under the name ETADEP Foundation. In the mid-1980s, some agricultural development work was started in the catchment, and cattle were distributed for use in ploughing muddy paddy fields. In about 1985, work began on the construction of an irrigation system. Some transmigration also took place, mostly from within the local area.

At the beginning of this century, Timor-Leste resumed the independence it had declared in 1975, immediately before it was invaded by Indonesia. In 2015, the governments of Timor-Leste and Indonesia entered into a Memorandum of Understanding on the Forestry Sector, as the first step of a commitment to manage shared natural resources jointly. One of the areas of cooperation for which the MOU provided was the management of cross-border catchments. In 2019, the two governments developed the Talau-Loes Management Plan Integrated Flow River Area or RPDAS. In 2020, the Global Environment Facility and the two governments initiated the Management of Indonesian and Timor-Leste Transboundary Watersheds project, with the objective of ensuring "... collaborative management of freshwater ecosystems and protect water, food and livelihood security..." in the catchment and another cross-border catchment.

Catchment

The river combines with its tributaries to make up Timor-Leste's largest river system. Its catchment or drainage basin has a total area of approximately, including part of the province of East Nusa Tenggara in Indonesia.
The East Timorese portion of the catchment is the largest of that country's catchments, but sources vary as to its size. Sources published before 2020 state that the East Timorese portion has a total area of , and that about 9% of the catchment lies in Indonesia. However, according to the official description of the MITLTW project, published in 2020, about of the catchment sits within Timor-Leste and approximately of it falls within Indonesia, where it is known as the Talau River catchment.
Timor-Leste has been broadly divided into twelve 'hydrologic units', which are groupings of climatologically and physiographically similar and adjacent river catchments. The East Timorese portion of the Talau/Loes catchment is the only major catchment in the Loes hydrologic unit. Of the ten transboundary catchments in the Indonesia/Timor-Leste border area, the Talau/Loes catchment is the largest, and has the greatest water use and accessibility.
The baseline scenario for the two catchments the subject of the MITLW project, including the Talau/Loes catchment, is characterised in the project documentation as: "continuation of poorly managed land uses, particularly agriculture, grazing and other activities degrading and removing forests/vegetation, which then contribute to soil degradation and loss, uncontrolled water flows, and associated deterioration in food and water security." The project aims to implement over a five-year period an alternative scenario achieving better protection of food, water and livelihood security within the two catchments.
In Indonesia, the Talau/Loes catchment covers 10 districts and 61 villages in Belu Regency. In Timor-Leste, it ranges across 19 administrative posts and 120 sucos in six municipalities, namely Aileu, Ainaro, Bobonaro, Cova Lima, Ermera and Liquiçá., the catchment's population was around 191,000 in the Talau portion and 163,000 in the Loes portion, or about 354,000 in total. Its upstream sector is a water conservation area with a very small population. Its midstream is the most densely populated sector, and is used for transportation and water extraction. Its downstream links to and supplies water and sediment flows into Timor-Leste's mainland and coastal ecotone area.
The catchment's elevation ranges from AMSL to sea level in the Talau portion, and from between and AMSL to sea level in the Loes portion. Its topography is dominated by slightly steep to steep slopes. The dominant form of drainage system in the catchment is parallel pattern drainage.
The catchment has a monsoon type climate, with a clear distinction between just two seasons, rainy and dry. The rainy season lasts about 6–7 months each year, and annual rainfall depends upon elevation and location. Over the catchment as a whole, average annual rainfall is around, and is more than offset by high evaporation averaging per annum. In the upper reaches of the Talau River, it is between and, and in the midstream of that river, it ranges from to. In the upstream Loes River area, it can be more than, in the midstream it is around, and downstream it is between and.
According to a rapid appraisal of part of the Indonesian portion of the catchment published in 2008, the main hydrological concerns of the stakeholders in that area were sensitivity to climate variability, imbalance of water demand and supply in dry periods, and soil erosion that could cause further degradation to the landscape. The overall pattern of river flow was described as having three phases: the early part of the rainy season when the soil and landscape water storage capacity was recharged, the second part when a larger proportion of the rainfall was transmitted to the river, and the dry season when water flow depended on the gradual release of stored water. The report of the appraisal suggested catchment improvement activities such as water harvesting during the rainy season using semi-constructed ponds; soil management in the form of terracing and infiltration pits in tree-based systems, to avoid further soil degradation, and the planting of trees.
Another rapid assessment, conducted in 2019, reported that there were several threats impacting the catchment. They included climate change and increasing variability in water availability; insufficient recharge areas; geomorphology that facilitated erosion, sedimentation and flooding; land use conflicts and over-exploitation of resources; and deforestation and land degradation. At the end of the 20th century, the total area of tree cover on the catchment's surface was more than 75%, but by 2019 it was down to only around 22%. Additionally, the catchment's low water availability baseline combined with poor soil and land management to result in low discharge and insufficient water reserves. Other hazard risks included biophysical vulnerability.