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Title: The water balance components of undisturbed tropical woodlands in the Brazilian cerrado

item SANCHES OLIVEIRA, P. - Universidad De Sao Paulo
item WENDLAND, E. - Universidad De Sao Paulo
item Nearing, Mark
item Scott, Russell - Russ
item ROSOLEM, R. - University Of Bristol
item DA ROCHA, H. - Universidad De Sao Paulo

Submitted to: Hydrology and Earth System Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2015
Publication Date: 6/22/2015
Citation: Sanches Oliveira, P., Wendland, E., Nearing, M.A., Scott, R.L., Rosolem, R., Da Rocha, H. 2015. The water balance components of undisturbed tropical woodlands in the Brazilian cerrado. Hydrology and Earth System Sciences. 19:2899-2910.

Interpretive Summary: The tropical forests, savannas, biological diversity and freshwater resources of Brazil are among the world’s largest. The Brazilian Cerrado is considered one of the most important Brazilian biomes, covering an area of 2 million km2, and is the second largest biome in South America after the Amazon. The physiognomies of the Cerrado vary from grassland to savanna to forest. Because of its endemic plant and vertebrate species, this biome has been classified as one of the 25 global biodiversity hotspots. Despite the importance of the Brazilian Cerrado, knowledge of hydrological processes and water budget dynamics associated with the change from native cover to grassland and cropland is still limited. In this study, we measured components of the water budget on a native Cerrado and bare soil site. We found that runoff increases and infiltration decreases on agricultural lands as compared to the native vegetation. These results are important for better understanding how to manage change in Brazil as more and more land is being converted to agricultural use.

Technical Abstract: Deforestation of the Brazilian cerrado region has caused major changes in hydrological processes. These changes in water balance components are still poorly understood but are important for making land management decisions in this region. To better understand pre-deforestation conditions, we determined the main components of the water balance for an undisturbed tropical woodland classified as “cerrado sensu stricto denso”. We developed an empirical model to estimate actual evapotranspiration (ET) by using flux tower measurements and vegetation conditions inferred from the enhanced vegetation index and reference evapotranspiration. Canopy interception, throughfall, stemflow, surface runoff, and water table level were assessed from ground measurements. We used data from two cerrado sites, Pé de Gigante (PDG) and Instituto Arruda Botelho (IAB). Flux tower data from the PDG site collected from 2001 to 2003 were used to develop the empirical model to estimate ET. The other hydrological processes were measured at the field scale between 2011 and 2014 at the IAB site. The empirical model showed significant agreement (R2 D0.73) with observed ET at the daily timescale. The average values of estimated ET at the IAB site ranged from 1.91 to 2.60mmday''1 for the dry and wet seasons, respectively. Canopy interception ranged from 4 to 20%and stemflow values were approximately 1%of the gross precipitation. The average runoff coefficient was less than 1 %, while cerrado deforestation has the potential to increase that amount up to 20-fold. As relatively little excess water runs off (either by surface water or groundwater), the water storage may be estimated by the difference between precipitation and evapotranspiration. Our results provide benchmark values of water balance dynamics in the undisturbed cerrado that will be useful to evaluate past and future land-cover and land-use changes for this region.