With a geographical size of 3,577 square kilometres, Lagos State is one of the smallest states in Nigeria, representing 0.4% of the entire geographical area Nigeria. Lagos State is located on the South-Western part of Nigeria on the narrow Coastal flood plain of the Bight of Benin.
Lagos State has an area of 356,861hectares, out of which 75,755 hectares are wetlands with the dominant vegetation of tropical swamp forest, comprising fresh waters and mangrove swamp forests. It shares a double rainfall pattern, with two climatic seasons – Dry (November-March) and wet (April-October). The drainage system of the State is characterized by a maze of Lagoons and waterways which constitute about 22% or 787 sq. km of the State total landmass.
The state has the highest population in the country, with over five percent 5% of the national estimate. The 1991 National Census figures put the population of the State at 5,725,116, out of a national estimate of 88,992,220. The UN Habitat Study and the UNDP assisted state Regional Master Plan estimated Lagos State population in year 2000 at 13.4million and over 15 million inhabitants in 2004.
The recent UN study (1999) expected the City of Lagos to hit the 20million population flux in Year 2010, thus progressively reaching 24.5million population in year 2015, at which time Lagos will be the third most populous city in the world. Thus Lagos population is growing ten times faster than New York and Los Angeles, with grave implication for urban sustainability.
The major water bodies in the state are the Lagos and Lekki Lagoons, Yewa and Ogun Rivers. The raw water supply is obtained by the Lagos Water Corporation (LWC) mainly from two rivers, the Iju and the Owo (170,000 and 265,000 m3 per day respectively).
The location of the state within the coastline implies that it is vulnerable to climate change, while its high urban population implies that provision of potable drinking water by the state’s water utility- the Lagos Water Corporation will be a major challenge.
The Lagos Water Corporation is in charge of supplying drinking water services to all parts of urban and semi urban areas of the state. However, the size and growth rate of Lagos means that needs are growing very rapidly.
The LWC currently has an installed water supply capacity of 160 million gallons per day (MGD) (712.9 million litres per day (MLD)), but ageing supply lines, water works and poor public electricity hamper the services of the corporation, hence it is operating at only 48% capacity, or only 36% of water demand. It supplies water to about 60% of the population. Only about 4million of the state’s 15million population have access to piped water.
The general shortage of water supply that is a result of this low capacity utilisation is then met by privately operated tankers, porters and privately owned boreholes and wells. This in turn has its own issues with regards to water purity standards, higher delivery costs and the ultimate impact on the state’s water levels from the improper tapping of ground water reserves and wastage in its collection and delivery.
The LWC believes that between 2000 and 2025 demand for potable water will grow from 200 to 1,200 million gallons per day (MGD), capital investment of US$100 million per annum will be required in order to reach 80% coverage.
Water is involved in all components of the climate system (atmosphere, hydrosphere, cryosphere, land surface and biosphere). Therefore, climate change affects water through a number of mechanisms. Water supply services are highly vulnerable to drought, extreme precipitation, and sea level rise.
Nigeria is likely to experience an increase in global warming from 1.4 °C to 5.8°C over the period 1990 to 2100. This national increase in atmospheric temperature and an increase in surface water temperature may also cause a decreased flows in Ogun/Osun River Basins caused by longer and more frequent dry seasons; and a reduction in dissolved oxygen content, mixing patterns, and self purification capacity and increase in algal blooms respectively Ogun/Osun River Basins. The Lagos Water Corporation sources it’s raw from these basins.
The changing climate is likely to exacerbate water management problems in Lagos generally through rising sea levels in the costliness, variable rainfall and extreme events like floods. Increase in inter annual Precipitation variability will evidently increase the difficulty of flood control and reservoir utilization during the flooding season.
Last year, several semi urban areas in the state were flooded by excess water released from the Oyan dam. A flood alert was issued few weeks ago, requesting residents of these villages to evacuate because of impending floods. Such intense extreme floods will obviously affect water quality and water infrastructure integrity, and increase fluvial erosion which introduces different kind pollutants to water resources.
Shifts in precipitation may result in changes in water availability and a reduction of stored water in Lagos Water Corporation Adiyan and Iju reservoirs fed with seasonal rivers, increased evapotranspiration will reduce water availability and result in salinisation of water resources and lower groundwater levels.
Other likely risks of climate change on water supply in Lagos state include the following:
- Variance in precipitation will significantly affects quantity and quality of water supply in the state.
- Impervious sandy Lagos surfaces and increased precipitation intensity may overwhelm current drainage systems in the state.
- Increased precipitation intensity and variability are projected to increase the risks of flooding and/or drought in many areas of the state and exacerbate many forms of water pollution.
- Higher water temperatures and changes in extreme including floods and droughts, are projected to affect water quality. Globally, the negative impacts of future climate change or freshwater systems are expected to outweigh the benefits
- Changes in water quantity and quality due to climate change are expected to affect food availability, stability, access and utilization.
- Climate change may affect the function and operation of existing water infrastructure in Lagos state – including hydropower, – as well as water management practices.
- Climate change challenges the traditional assumption that past hydrological experience provides a good guide to future conditions, therefore the consequences of climate change may alter the reliability of current water management systems and water-related infrastructure.
What adaptation and mitigation strategies should the Lagos Water Corporation and similar water utilities in Nigeria should adopt to cope with this problem?
- It is essential that the Lagos State Government incorporates of information about current climate variability into water- related management would assist adaptation to longer-term climate change impacts.
- LWC should take measures to reduce water theft and leakages
- LWC should take measures to Adjust water-intake locations
- Lagos Water Corporation should ensure that Communities and Households are trained on rainwater harvesting and water reuse techniques.
- Construction of dry toilet/ecosanitation model systems should be promoted to reduce water use.
- Generally, integrated demand-side as well as supply-side strategies should be adopted to ensure water supply during average and drought conditions.
From the foregoing, it is obvious that Lagos state is likely to be adversely affected from climate change. The challenge remains the capacity of appropriate agencies to effectively explore the possible extent of the impact, discuss what can be done to reduce the adverse effects, and make policy reviews and development to address the impacts.
However, current water management practices of the Lagos Water Corporation, may not be robust enough to cope with the impacts of climate change on water supply reliability, flood risk, health, agriculture, energy and aquatic ecosystems. Therefore to address these challenges the Lagos State Water Corporation needs to set up a Desk on Climate change to study the likely effects of climate change on water supply in Lagos state and come up with mitigation and adaptation strategies.
The worst effects of climate change related disasters such as floods and droughts can be avoided with proper water management, and that investment in water management is a non-regret adaptation strategy.
The challenge therefore falls on water stakeholders in Lagos in particular and Nigeria as a whole to promote progressive and integrated water and climate change policy at state and national levels, through targeted advocacy, working with other to develop policy recommendations, statements and interventions as well as co-ordinating events, seminars and workshops.