Written by CHARLES NKULA
Development experts say poverty amidst the populations surrounding Malawi’s second largest water body, Lake Chilwa, has placed the lake under threat.
Dr. Rodney Lunduka, an environmental research expert with the London based International Institute for Environment and Development (IIED), says that competition for natural resources has exerted pressure on the lake and its catchment area. He observes that poor populations surrounding Chilwa have over the past decades increasingly depended on the lake’s wetlands natural resources for survival.
“Competition between users for water and watered lands has intensified over the past decade or more,” he says adding that the use of water further upstream by Zomba and its expanding peri urban areas as well as the negative downstream effects of high level of pollution from several urban sources contribute to the lake's challenges.
Lake Chilwa, Africa’s twelfth largest lake, has a basin that provides livelihood opportunities to more than 117, 031 families with its resources such as water, fish and birds. It also provides grass for thatching houses and making boats, mats, fish traps, birds’ traps and baskets.
The lakes catchment area alone directly supports more than 77,000 households who utilize it for fishing, irrigation, birds hunting and rain fed agriculture. Water from the tropical lake that has no outlet is also used for transport and domestic purposes.
Lunduka observes that “due to increase in drought incidences and erratic rainfall as a result of climate change, irrigation has been promoted and more land is being cleared go grow more rice and irrigated maize.
“This has increased soil erosion causing siltation and reduced water flowing into the lake there by reducing fish productivity,” he notes.
Lunduka says that in economic terms benefits derived annually from the lake and its riparian wetland amounts to US$ 19 million or US$21,305/km2 of the wetland.
“With 77,000 people living in the wetland, its value translate into benefits of US$242 per wetland inhabitant,” he says, explaining that “the main reason for the recognition of increased value in the watered areas is that while watered land had long been recognised as an important strategy to improve family food security and income, it has gained even more value in people eyes in the wake of the drought and floods in the past two decades.”
Earlier in the year, Malawi’s irrigation expert Dr.Henri Njoloma said that a changing rainfall pattern in the country due to climate change resulting in uneven and unpredictable rainfall distribution has contributed to the reduced productivity of natural resources such as land and water.
“It's been found that rainfall distribution characteristics have changed over time becoming more unpredictable and, hence, reducing production,” says Njoloma. “In general, every time there is an erratic rainfall pattern, maize production is affected.
The irrigation expert recommends building more sustainable irrigation systems so that agricultural production can withstand drought. He also recommends removing policies that depends on rain-fed food production and economic activities to control the problems associated with the changing rainfall pattern.
Lunduka echoes Njoloma’s sentiments: “Without aggressive water harvesting and management, Malawi is likely to remain poor due to uncertainty of the rainfall regime. Developing countries, such as Malawi, will be more vulnerable to climate change mainly because of the larger dependency of their economy on agriculture.”
He emphasizes the importance of assessing vulnerability of water resources to climate change at watershed levels for water resources sustainability.
Lunduka warns that the changes in rainfall and temperature could've far reaching consequences on the water resources of Malawi as well as the country’s economy which is based on agriculture.
The development expert estimates that the loss in value due to reduction in fish productivity in Lake Chilwa is about US$ 1,003,580 per year. “An additional US$ 249,460/year is lost on site in irrigation lands due to loss in soil fertility and siltation,” he says noting that to supplement their income after crop failure or reduction in fish catches, communities in the catchment have increased bird hunting and making crafts.
“An increase in bird hunting is causing an estimate loss of US$59,238 per year from reduction in birds’ population,” he says. “An additional US$8,473,433/year worth of food crops is estimated on top of eliminating the losses to fisheries and birds resources”.
He recommends proper and strategic planning and implementation of climate change adaptation strategies in the lakes catchment area to ensure positive benefits and increased efficiency of downstream adaptation strategies.
However, he observes that efforts to estimate the cost and benefits of the adaptation strategies haven't been straight forward because in many cases the climate change impacts are on natural capital whose boundaries extend beyond project boundaries. “Therefore, projects or adaptation activities may have impacts beyond their boundaries affecting other stakeholders using the capital resource directly or indirectly,” he says.
The 2,400 km2 lake, which varies considerably in size depending on precipitation in the catchment, is situated southeast of Lake Malawi and Lake Malombe. 1,500km2 is open water while 578km2 is in swamps and marshes and 580km2 is grassland which becomes inundated seasonally. Its catchment of 8,349km2 is shared between Malawi (5,669km2) and Mozambique (2,680km2).
Five major rivers, Domasi, Likangala, Thondwe Namadzi and Phalombe drain into Lake Chilwa from the Shire highlands and Zomba mountain contributing 70% of total inflow to the lake. From Mozambican side, three rivers namely Mnembo, Mbungwe and Nchimadzi drain into the lake.
The four to five meter shallow lake contains 14 species of fish of which 3 hardy species are more abundant Mlamba (Clarias gariepinus), Matemba (Barbus paludinosus) and Makumba (Oreochromis shiranus chilwae). The fish in the lake move seasonally between the lake and its tributary rivers. At peak level about 6,000 men are engaged in small scales fishing activities which are valued up to US$17 million per year, notes Lunduka.
He says that the value of the lake also accrues to middlemen and marketers. “Its mean annual value is more than 10 times as high as the value of harvest from rice fields, the second most important activity in the wetland area” he says. Lake Chilwa has about 160 species of resident and 41 species of palearctic migrant waterbirds respectively. About 22 species of palearctic birds are regular visitors to Lake Chilwa between September and April every year.
It supports about 23 species including the African Spoonbill Platalea alba, Fulvous Whistling Duck Dendrocygna bicolor, Black-headed Heron Ardea melanocephala and secretive marsh birds like Lesser Moorhen Gallinula angulata and Lesser Gallinule Gallinula alleni which qualifies the catchment for the Ramsar criterion of 1% level of individuals per population.
The total waterfowl population of Lake Chilwa is estimated at a conservative figure of about 354,000. Predators such as the resident Pinkbacked Pelican Pelecanus rufescens, the Grey-headed Gull Larus cirrocephalus and the migrant White-winged Black Tern Chlidonias leucoptera are common in the open water, especially in Kachulu Bay, a major fishing centre.
Birds of prey found on the lakes wetland include the African Marsh Harrier Circus aeruginosa and the much less common Fish Eagle Haliaetus ranivorus. Others include the Yellow-billed Kite Milvus aegypticus, the Lesser Kestrel Falco naumannii and the palearctic migrant birds of prey.
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