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

Abstract

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 (R 2 = 0.73) with observed ET at the daily timescale. The average values of estimated ET at the IAB site ranged from 1.91 to 2.60 mm day −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.

Effects of conversion of native cerrado vegetation to pasture on soil hydro-physical properties, evapotranspiration and streamflow on the Amazonian agricultural frontier

“…Studies evaluating the impacts of land-use change on hydrological processes in the Amazon are relatively common [16–21]. However, assessments of the environmental impacts of the Cerrado conversion into agro-pastoral landscapes are scarce [22–24] despite the importance of the cerrado in provisioning and maintaining ecosystem services such as adequate water quantity and quality [25–27]. Although studies show that land-cover change in the Brazilian Cerrado alters the water balance, e.g.…”

“…by increasing streamflow [28,29], they do not allow generalizations since they are based mostly on low-resolution datasets. In this biome, water balance components such as streamflow and infiltration, and soil physical properties are poorly understood, especially at field scale in the Cerrado [24,30]. Furthermore, the scarcity of hydrometeorological data and the lack of information on vegetation and geological characteristics are major limitations for a reliable quantification of these land-use change effects.…”

Improved Albedo Estimates Implemented in the METRIC Model for Modeling Energy Balance Fluxes and Evapotranspiration over Agricultural and Natural Areas in the Brazilian Cerrado

“…Figure 7b shows that the estimated ETa varied between 2.48 and 6.56 mm day −1 with the same seasonal pattern verified on the USR site, despite having higher values. For this area, Reference [52] observed ETa values varying from 1.0 mm day −1 (dry season of 2010) to 7.1 mm day −1 (summer season of 2012), and Reference [4] ETa estimates for the USR site (Figure 6a) are close to the 1:1 line, with some estimate deviations during the rainy season. It is important to point out that for these dates it was difficult to select suitable hot pixels for the internal calibration, because the agricultural areas were almost entirely covered with the sugarcane crop.…”

“…Thus, the conversion of undisturbed cerrado to grass-dominated or agricultural crops (combined with a higher fire frequency) has the potential to change the energy balance by increasing surface albedo and temperature [10], as well as water balance, by increasing runoff and groundwater recharge, decreasing canopy interception and reducing ET due to less water uptake by deep roots (especially during the dry season).Therefore, assuming the local precipitation is reliant on regional rates of ET, the cerrado climate could become drier [4,39,52,87]. Lastly, as the Brazilian Cerrado is a large biome with different conditions of land cover, soil types, vegetation, and hydrometeorology, it is necessary to carry out more studies in different regions in order to improve our understanding of ET dynamics.…”

Alternativas de restauração de florestas ripárias para o fornecimento de serviços ecossistêmicos.

“…Estes resultados são sustentados por pesquisas que indicam que a cobertura florestal age como atenuante para vazões de pico, promovendo maior evapotranspiração e infiltração do solo, diminuindo ou mesmo extinguindo o escoamento superficial na bacia hidrográfica (PIERCE, 1965;ROCHA, 2003;DE FREITAS et al, 2013;MOLIN, 2014;OLIVEIRA et al, 2015). …”