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The Effects of Forest Cover on Baseflow Characteristics of Streams in the Mountainous Interior of Puerto Rico
Project Number: 2516-DKQ00
Although there have been numerous investigations of the effects of land-cover changes on the magnitude and frequency of peak stream runoff, very few studies relate land use changes to stream baseflow characteristics. The few studies relating the changes in forest cover with the magnitude and frequency of baseflows have been restricted to areas in overlying coastal/alluvial aquifers in temperate climates where the removal of forest cover has resulted in an increase of the low flow in the adjoining stream(s). According to the published literature, few studies of the relation between baseflows and land-use changes have been done in mountainous watersheds at high altitudes where climatic and related hydrologic parameters are significantly different from watersheds at lower elevations (such as coastal alluvial valleys).
An understanding of how land-use changes such as deforestation or afforestation might affect baseflow characteristics is of utmost importance. Baseflows constitute the sole streamflow component during the annual dry season with minimum or no rainfall that can generate runoff. Baseflow is defined as the background discharge of a stream between floods and is supplied by inflow of groundwater. During the annual dry season, which in Puerto Rico usually lasts from January through March, baseflow is the only water-supply source for human consumption available from streams. Also, during the dry season, baseflows are necessary to maintain the stream biologic diversity as well as the capacity to assimilate the discharge of organic wastes.
Considering the increased popularity of agricultural practices that require the removal of forest cover, such as the replacement of shade coffee with sun coffee at elevations from about 1000 to 3000 ft, a study is needed that explores the probable relation between forest cover and baseflows characteristics as explained above. This study will help the Puerto Rico Department of Natural and Environmental Resources (PRDNER) and other state and federal agencies to reconcile their current management plan to increase the island’s total acreage in forest cover including the large-scale reforestation effort presently underway, with the preservation and enhancement of the streams as reliable water-supply sources and viable ecosystems. The results of this study may also help the Puerto Rico Department of Agriculture to encourage changes in agricultural practices in order to minimize the loss of high base-flow generating capacities of the highlands in the mountainous interior of Puerto Rico.