Adapting water resources systems to climate change in tropical areas: Ecuadorian coast

Climate change is expected to increase rainfall and temperature in the tropical areas of the Ecuadorian coast. The increase in temperature will also increase evapotranspiration therefore, future water balance on Ecuadorian coast will have a slight variation. Changes in precipitation patterns and evapotranspiration will produce an increase in the water requirements for current crops, so an imbalance in the water resources systems between natural resources and water demands is expected. This study presents water resources management as an adaptation measure to climate change for reducing vulnerability in tropical areas. Twelve bias-corrected climate projections are used, from: two AR5 General Circulation Models (GCMs), two Representative Concentration Pathways, 4.5-8.5 scenarios, and three time periods, short-term (2010-2039), medium-term (2040-2069) and long-term (2070-2099). These data were incorporated into the Lumped Témez Hydrological Model. Climate change scenarios predict for the long-term period both a mean rainfall and temperature increases up to 22%-2.8 °C, respectively. Besides, the potential evapotranspiration will increase until 12% by Penman-Monteith method and 60% by Thornthwaite method. Therefore, natural water resources will finally have an increase of 19% [8-30%]. Additionally, water requirements for crops will increase around 4% and 45%. As this research shows, in tropical regions, currently viable water resources systems could become unsustainable under climate change scenarios. To guarantee the water supply in the future additional measures are required as reservoir operation rules and irrigation efficiency improvement of system from 0.43 to 0.65, which it involves improving the distribution and application system. In study area future irrigation areas have been estimated for 13,268 ha, which under climate change scenarios is unsustainable, only 11,500 ha could be expanded with a very high irrigation efficiency of 0.73. Therefore, in tropical areas the effect of climate change on expansion projects for irrigated areas should be considered to ensure the functioning systems.

Linking El Niño Southern Oscillation for early drought detection in tropical climates: The Ecuadorian coast

El Niño Southern Oscillation (ENSO) is the most determining climate pattern in the tropics of the Pacific coast of America that regulate flood and drought periods. Over the last decades, Ecuador has incurred in significant economic losses due to drought events, around 4% of the GDP, mainly in the agricultural and livestock sectors and the hydropower generation. The use of Drought Indicators and the Early Drought Detection can contribute to reduce the impacts of these events. A drought forecasting system, based on ENSO and Drought Indicators, is presented to determine the possibility of appearance of drought events in Manabí River Basin District (MRBD). This system can help to the decision makers, in December (short-term drought, seasonal) and in May (long-term drought, annual), to activate the drought measures in the following months. Six climate indices are used for ENSO: Oceanic Niño Index (ONI), Southern Oscillation Index (SOI), and Sea Surface Temperature (SST) for Niño regions: 4, 3.4, 3 and 1 + 2. On the other hand, two drought indices are used: spatially distributed Standardized Precipitation Index (SPI) -1, 3, 6 and 12 months-, and a modified Palmer Drought Severity Index (PDSI), derived from a calibrated water balance model. This system allows early drought detection, assessing SST 1 + 2 (lag -7), 3 (lag -9) and 3.4 (lag -9) anomalies and drought indices, in December for a season drought and May for an annual drought. These analyses demonstrates that, drought may forecasting up to 7-9 months before their occurrence, through SST regions observations, based on strong relationship between ENSO and droughts occurrence.