Tempisque-Bebedero Basin (Costa Rica)
The river flows reflect the seasonal climate. Mean flows from 1973 to 2003 at Guardia, Tempisque River and Tenorio, Bebedero River gauging stations (see discharge graph below) were 24.6 and 9.3m3/s, respectively. However, the lowest dry season flows measured (late April) were as low as 2.6 and 2m3/s, respectively. The mean water yield of 5.3 l/s per km2 at Guardia are among the lowest in the country. Such a marked seasonality with relatively low water yields has historically been a challenge for water resources management in the northwestern region of Costa Rica. The overall mean annual water balance for the catchment system is: precipitation of around 1800mm/year, MODIS satellite-derived actual evapotranspiration equals around 1100mm/year and the resulting runoff is 700mm/year.
Additionally, to a marked hydrometeorological seasonality (rainfall and river runoff exhibit dry and wet season cycles), the Tempisque and Bebedero rivers show a pronounced year-to-year variability in their total runoff volumes synchronous to rainfall. This variability can be related to regional circulation patterns such as the El Niño Southern Oscillation (ENSO) and also to indirect effects of tropical storms (Waylen, 1996). The strongest historical El Niño events (1983, 1987, 1997) are reflected in the lowest annual runoff (~400mm/year) and La Niña events in combination with strong tropical storms (for example, 1988) in the highest recorded runoff volumes (>1200mm/year). The latter highest volumes exceed the drier years for more than three times, which has resulted in flood issues across the low relief plains before reaching the natural floodplain wetland areas (Palo Verde National Park).
References and further reading:
Fondo Nacional de Financiamiento Forestal FONAFIFO (2012) Estudio de cobertura forestal de Costa Rica 2009-2010.
Instituto Nacional de Estadística y Censos, INEC (2014) VI Censo Nacional Agropecuario.
Magaña, V., Amador, J.A., and Medina, S. (1999) The midsummer drought over Mexico and Central America. J. Climate, 12 (1967): 1577-1588, doi: http://dx.doi.org/10.1175/1520-0442 (1999)012<1577:TMDOMA>2.0.CO;2.
Peel, M. C., Finlayson, B. L., and McMahon, T. A. (2007) Updated world map of the Köppen-Geiger climate classification. Hydrol. Earth Syst. Sci., 11, 1633-1644, doi:10.5194/hess-11-1633-2007.
Tecnológico de Costa Rica, TEC (2014) Altas de Costa Rica.
Waylen, M.E. (1996) Interannual variability of monthly precipitation in Costa Rica. J. Climate, 9: 2606-2613, doi: http://dx.doi.org/10.1175/1520-0442(1996)009<2606:IVOMPI>2.0.CO;2.
WorldClim global product: http://www.worldclim.org/tiles.php?Zone=23