A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

High resolution, runoff and discharge fields of theAmazon basinBalázs M. Fekete, Charles J. VörösmartyWater Systems Analysis GroupInstitute for the Study of Earth, Oceans, and SpaceUniversity of New Hampshire39 College Road, Morse Hall, Durham, NH 03824, USAbalazs.fekete@unh.edu / charles.vorosmarty@unh.eduAccurate representation of the spatially distributed runoff and discharge are essentialinformation for a wide variety of ecosystems studies. Terrestrial runoff can be estimated fromclimate variables (such as air temperature, precipitation, vapor pressure, solar radiation, etc.)but such estimates are often inaccurate due to the inherited errors originated from the inputdata.River discharge (which is an integrated signal of the runoff) is one of the most accuratelymeasured components of the hydrological cycle, but it is limited to selected locations whereriver discharge is measured. A combination of the water balance model estimated runoff andmeasured discharge has the potential to provide the most accurate assessment of theterrestrial runoff and discharge in non-monitored sections of the river systems.The Water Systems Analysis Group of the University of New Hampshire developed a simpletechnique to combine water balance model simulated runoff with measured discharge. Thedischarge monitoring stations are co-registered to gridded network, which allows theestablishment of station topology (i.e. the next station downstream from each station) and thedelineation of inter-station areas (the catchment area between upstream gauges and thedownstream station). Correction to water balance model simulated runoff is applied in eachof the inter-station regions to correct for inconsistency between simulated runoff andmeasured discharge. This technique was successfully applied at a global scale first using 30-minute network and discharge data from the Global Runoff Data Centre, Koblenz, Germany.New regional versions of the composite runoff fields were developed recently for theAmazon basin at 6' and 15' resolutions using climate forcings from various sources (such asthe Climate Research Unit of University of East Anglia, the GEWEX Global PrecipitationClimatology Project) and river discharge data from Agência Nacional de Energia Elétrica(ANEEL). The new regional composite runoff fields were developed as a time series for the1979-99 period at monthly time steps. The composite runoff fields were aggregated torepresent river discharge using a special routing scheme, which allows dischargeinterpolation between discharge gauges with the aid of the runoff fields. Such discharge fieldsprovide accurate assessment of river discharge everywhere along the Amazon basins, whichis constrained by the measured discharge at gauging stations.The 6' and 15' minute networks and the composite runoff and discharge fields are to bereleased to the scientific community after rigorous testing. Further development will focus onautomating the input data processing, so similar composite data products can be developedsemi real-time, when the input data (such as the climate forcings and the observed discharge)are available.