Service Contract No 2007 / 147-446 Strategic ... - Swaziland

5.2.2.2 Expected effects of climate change on the water regimeThe IPCC has published several key reports and assessments on climate change and triedto predict a future state using complex climatic models. Water is involved in all componentsof the climate system (atmosphere, hydrosphere, cryosphere, land surface and biosphere).Therefore, climate change affects water through a number of mechanisms.Observed warming over several decades has been linked to changes in the large-scalehydrological cycle. There is significant natural variability – on inter-annual to decadal timescales– in all components of the hydrological cycle, often masking long-term trends. There isstill substantial uncertainty in trends of hydrological variables because of large regionaldifferences, and because of limitations in the spatial and temporal coverage of monitoringnetworks.Current national water management practices may not be robust enough to cope with theimpacts of climate change on water supply reliability, flood risk, health, agriculture, energyand aquatic ecosystems. In most of the country, existing water management practicescannot satisfactorily cope even with current climate variability, so it is not uncommon for floodand drought conditions to damage infrastructure (pump stations and other abstraction points)and strain water availability. As a first step, improved incorporation of information aboutcurrent climate variability into water-related management would assist adaptation to longertermclimate change impacts. Climatic and non-climatic factors, such as growth of populationand damage potential, would exacerbate problems in the future.Among the most important drivers of water use are population and economic development,but also changing societal views on the value of water. The latter refers to the prioritisation ofdomestic and industrial water supply over irrigation water supply and the efficient use ofwater, including the extended application of water-saving technologies and water pricing.The dominant non-climate-change-related drivers of future irrigation water use are: the extentof irrigated area, crop type, cropping intensity and irrigation water-use efficiency.Recognising and accepting the science and predictions of climate change published by theIPCC, climate change may also influence efficiency of the Swazi sugar sector 11 . Sugar caneis a water-intensive crop and its growth is directly related to rainfall, temperature and wateravailability. All sugar cane in Swaziland is grown under irrigation, thus reducing vulnerabilityto climate change, but exerting further pressure on available water sources. Also crop growthis closely related to temperature: optimum temperature for sprouting of stem cuttings is 32-38ºC, slowing down below 25ºC, reaching plateau level at 30-34ºC, reduced above 35ºC andpractically stopping above 38ºC. However, for ripening temperatures between 12-14ºC aredesirable, as it influences the reduction of vegetative growth rate and enrichment of sucrosein cane; at higher temperatures reversion of sucrose into fructose and glucose may occur,leading to less accumulation of sugars.The presence of pests and changes in their distribution patterns will also change withtemperature. For example, smut initiation and spread is high when ambient temperatures arein the range of 25-30ºC; the spread of red not disease is high in the temperature range of 37-40ºC (other conditions being similar); rust incidence is high when minimum temperatures arereduced. Insect pest activity could also be similarly affected by changes in temperature andhumidity. Sugar cane productivity and juice quality are influenced by weather conditionsduring the crop-growth sub-periods. Sugar recovery is highest with low humidity, brightsunshine hours, cooler nights with wide diurnal variations and very little rainfall during the11 The climate dependencies of sugar cane production and potential effects of climate change is mainly –but not exclusivelybasedon the document: Enabling Activities for the Preparation of Jamaica’s Second National Communication to theUNFCCC, Vulnerability and Adaptation Assessments Work Package 2: Water Resources and Agriculture, Final Report.RDMU (Strategic Environmental Assessment of the National Adaptation Strategy) - Page 46