The Role of Land Cover in the Propagation of Rainfall Into Streamflow Trends

Abstract

The replacement of natural forests with agriculture is generally associated with modifications in the hydrological behavior of a basin. This is particularly notable in the tropics and subtropics. Southern Brazil is a region with extensive agricultural production, forest conservation, and a vast unexplored streamflow data despite substantial rainfall trends observed in recent decades. In this work, we explore trends in the streamflow regime in the majority of the monitored basins in Southern Brazil. Additionally, we evaluate if pristine forested basins and agricultural nonforested basins have significantly different streamflow responses to changes in rainfall. We analyzed annual averages, maxima, minima, and seasonality of a 36‐year data set (1975–2010) of 675 rainfall and 140 streamflow gauges. Results reveal that large trends are widespread in Southern Brazil, especially in basins with areas smaller than 10,000 km2. Changes in the rainfall regime did not directly translate into changes in the streamflow regime. Changes in the annual maximum flow of forested basins were not statistically significant even when the annual average and maximum rainfall increased significantly. Correlations between changes in rainfall and streamflow for two indices, namely, duration of low‐magnitude events and seasonality, were statistically significant (p < 0.05) only for agricultural basins. The results indicate a higher propagation of hydrological changes through anthropogenically modified systems, providing evidence that agricultural basins are more sensitive to changes in the rainfall regime.

Climate, Irrigation, and Land Cover Change Explain Streamflow Trends in Countries Bordering the Northeast Atlantic

“…For example, in China it is suggested that a large proportion of observed reductions in streamflow can be attributed to land use and land cover changes (Li et al, ; Liu et al, ; Zhang et al, ). These effects are also observed in southwestern Australia (Liu et al, ), in tropical catchments in Puerto Rico (Beck et al, ), and in highly modified basins of Brazil (Chagas & Chaffe, ).…”

A systematic analysis of climate model precipitation in southern Brazil

“…Though, ENSO diversity leads to different responses in SB and models that cannot simulate the different types of ENSO are probably unable to correctly simulate precipitation variability and extremes in SB. Changes in extreme rainfall events have already been reported in both seasonal (Chagas and Chaffe, 2018) and annual scales (Fernandes and Rodrigues, 2018). SB precipitation is generally well distributed throughout the year.…”

Trend in hydrological series and land use changes in a tropical basin at Northeast Brazil

“…However, identifying the changing patterns in a hydro-meteorological series at the local level is complex, due to several active factors that can contribute, jointly or separately, for variations in stationarity patterns (Milly et al, 2008), in addition to the specific characteristics of the region, such as the size of the basins (Chagas and Chaffe, 2018).…”