Haiti – Dominican Republic - Disasters and Conflicts - UNEP

once again for the 1990-2009 period to an annualaverage temperature of 25.4°C. 96The Dominican Republic has experiencedsimilar temperature patterns as Haiti. Averagetemperatures in the Dominican Republic haveincreased by around 1.2° C from the 1930-1960to the 1960-1990 time period. Between the1960-1990 and 1990-2009 time periods, however,temperatures decreased by 0.3° C to a yearlyaverage of 24.7° C. 97In summary, climate change for Hispaniola isexpected to result in an overall drier and hotterclimate, with more severe dry seasons with lowerstream flows, and exacerbating existing health,social and economic challenges.HydrologyThe majority of the rivers in the mountainous regionsof Hispaniola are short and steep. This means thatwater flow rates at any particular time are governedmainly by recent rainfall (days to hours) rather thanannual rainfall. Flash floods can occur in a matterof hours and the same rivers can run almost dryfor two months in the dry season. Flow variations of100 times or more are not uncommon. The levelof responsiveness reduces with increasing size, thelarger rivers with large catchments are much morestable than the smaller rivers.At the national level Haiti has substantial fresh waterresources, divided between 30 main watersheds. 98However it also has national scale, chronic waterproblems including degraded catchments, waterscarcity, flooding and bacterial contamination ofwater sources.The different Departments of Haiti see major variationsin annual rainfall as a result of topography,prevailing winds and the sporadic nature of tropicalstorms and hurricanes. The wettest areas are thepeaks of the highlands along the southern coast,where rainfall can exceed 4000 mm, while thedriest areas are in the northwest Departments,where rainfall can drop to 350 mm per annum.All parts of the country experience a drier seasonfrom December to April.The Pedernales river, that forms the border in the southern part of the island, has a low water flow duringlarge parts of the year and is easy cross on foot. The water flow can, however, increase dramatically withinhours as a result of heavy rains falling in the mountains a couple of kilometers from the low lying coastalareas.© UNEPHaiti – Dominican Republic: Environmental challenges in the border zone25