Climate Change and Intense Irrigation Growth in Western Bahia, Brazil: The Urgent Need for Hydroclimatic Monitoring

Abstract

In Western Bahia, one of the most active agricultural frontiers of the world, cropland area and irrigated area are increasing at fast rates, and water conflicts have been happening at least since 2010. This study makes a hydroclimatic analysis of the water resources in Western Bahia, from both supply and demand viewpoints. Time series of precipitation for the period 1980–2015 and river discharge for the period 1978–2015 are analyzed, indicating a significant reduction of up to 12% in rainfall since the 1980s, and a reduction in river discharge in all stations studied, in both the rainy season and the dry season. Combined with that, irrigated area has increased over 150-fold in 30 years, and in the most irrigated regions, has increased by 90% in the last eight years only. Seven regions in Western Bahia have been identified where the potential for water use conflicts is critical. Moreover, the combination of reduced availability and increased demand of water resources indicates that, if current trends are maintained, conflicts over water may become more frequent in the next years or decades. A short-term alternative to avoid such conflicts is to largely avoid irrigation during the months with low discharge. However, a monitoring system in which the availability and demand of water resources for irrigation are actually measured and monitored, is the safest path to provide water security to this region.

Analysis of the long-term effects of groundwater extraction on the water balance in part of the Urucuia Aquifer System in Bahia - Brazil

“…The graphs of Figure 2 (A, B, C) represent the historical data of average monthly flows and average flows during 5-year periods of the Éguas, Arrojado and Formoso Rivers (ANA, 2019), showing a continuous decline since the 90's. This can be potentially explained by the decrease in rainfall (Pousa et al, 2019) and by an increase in surface water intakes for agricultural purposes, including irrigation (the flow-rate granted in 2017 was approximately 28 m 3 s -1 ). The other charts in Figure 2 shows the groundwater levels (WL) with respect to the ground surface (CPRM, 2019), compared to the rainfall (P) at the nearest station (ANA, 2019) (geographical position of the stations, see Figure 1).…”

“…It accounts for one-third of all agricultural wealth in Bahia (AIBA, 2018). Mechanized agriculture occurs in this region, and is often irrigated using superficial and subterranean water resources (Santos, 2016;Pousa et al, 2019).…”

Carbon stocks and dynamics of different land uses on the Cerrado agricultural frontier

“…The cropland area in this region expanded from virtually zero in 1985 to 690 thousand hectares of soybeans in 2000 to 1.6 million hectares in 2018, reaching production records of 6 million tons of soybeans and 1.245 million tons of cotton produced in the 2017/2018 harvest [36]. This rapid advance of agribusiness in Western Bahia exposed the natural resources to intensive anthropic pressure, raising concerns about the effects of land use change on regional water availability, landscape fragmentation, soil physical properties, and carbon storage [16,[37][38][39][40]. Previous studies have shown that suppression of native vegetation throughout the Cerrado domain caused nearly 200 Tg-C to be emitted between 2003 and 2008 (40 Tg-C yr −1 ) from areas converted to pasture [41] and an average of 179 Tg-C between 2003 and 2013 from areas converted to cropland (18 Tg-C yr −1 ) [42].…”

Climate Variability and Climate Change Impacts on Land Surface, Hydrological Processes and Water Management

“…However, in a recent period of 1997-2013, the impact of coal mining on streamflow reduction was dominant, reaching 29.88 mm (54.24%). Pousa et al [3] analyzed climate change and intense irrigation growth in western Bahia, Brazil and concluded that urgent management is required for hydroclimatic monitoring. They found that the irrigated area has increased over 150-fold in 30 years, and in the most irrigated regions, has increased by 90% in the last eight years only.…”