Climate change and water allocation – how to strike a balance
WATER IS a fundamental human need and an essential resource for socio-economic development and environmental protection. The management, protection and allocation of Jamaica’s freshwater resources, by virtue of the Water Resources Act (1995), is vested in the Water Resources Authority (WRA), a statutory body of the Government of Jamaica (GOJ). Intrinsic to the function of the authority is the allocation of water resources, which is the process of distributing water supplies to meet the various competing sectoral needs. The exploitable water resources are unevenly distributed across the island, while the overall level of stress on the island’s water resources is moderate. The Rio Cobre and Kingston basins the two most stressed basins.
CLIMATE 1
Notably, 84 per cent of the water supply in Jamaica is from groundwater resources, predominantly from limestone aquifers, and most of this water supply is used for agriculture in the Rio Minho and Rio Cobre basins. Surface water accounts for approximately 16 per cent of the water supplied to all sectors. The primary source of water in the country is rainfall, which provides flows in the streams, direct recharge to the limestone and alluvial aquifers, and indirect recharge to the aquifers through the streams.
CLIMATE 2
How will climate change impact our water resources?
Climate change is expected to modify the global hydrologic cycle and affect the temporal and spatial distributions of water availability. While the regional hydrologic changes cannot be predicted with accuracy, it is expected to negatively impact the availability of water resources islandwide through droughts, floods, reduced precipitation, increased temperature, and evapotranspiration. If these anticipated changes are realised, the two most sensitive sectors would be the agriculture and domestic sectors, the greatest consumers of the island’s water resources. Equally sensitive is the aquatic environment which must be given priority for the preservation and/or restoration of aquatic ecosystems on which we depend. Climate change will affect not only surface run-off into a stream, but also rates of evaporative loss, seepage to aquifer systems, recharge from those aquifers, and rate of consumptive use for domestic, agriculture and industrial uses. Additionally, saline intrusion of coastal aquifers is a likely effect of sea level rise, which may result in the abandonment of affected wells and the loss of existing water supply infrastructure.
HOW WILL THE WRA RESPOND?
The following changes will be implemented to the existing system for water allocation:
■ Currently, each licence application is processed by appropriating the approved volume from the existing unappropriated water in each basin, utilising two key assessments: the estimation of the total volume and distribution (spatial and temporal) of water resources in the basin, and the determination of water that is available for use at different times, utilising the historic observed flows or basin yields. All applications will now be considered using
climate change scenarios that take into consideration the uncertainties of climate change.
■ Conduct quantitative simulations through quantitative approach such as robust decisionmaking or the robust assessment model for water allocation, as well as determine the potential future mean annual run-off for basin catchments. This will allow the WRA to be more cautious in defining the amount of water available for allocation, allowing the varying of existing or newly appropriated licence to allowable consumptive volumes as climactic condition changes to avoid overallocation.
■ Review consumptive use rights. Currently, licences are granted for five years. The WRA is reviewing the possibility of varying the validity period for each licence from five to three years. This will allow the WRA to respond to the expected variations in streamflows and groundwater levels.
■ Strengthening of governance capacity. Documentation of water withdrawal and consumptive uses, and enforcement of conditions of the licence, are paramount. A key condition of all abstraction licence is the installation of flow-measuring device to determine the volume of water abstracted on a daily or monthly basis. This condition will be strictly enforced for abstractors or sources, to facilitate the development and maintenance of a more accurate inventory of water abstraction.
■ Improved human and institutional capacity and technical knowledge to ensure that new technologies are used in the management of our water resources.
The time has come for robust analysis, institutional strengthening and innovative thinking on water allocation to improve our capacity to adapt to the uncertain but potentially large impacts of global climate change on water resources. Jamaican can be assured that the WRA is mindful of existing climactic uncertainties and while there is no simple prescription for adaptation to climate change, the WRA will endeavour to strike a balance in the allocation of our freshwater resources.