Hydroclimatic change disparity of Peruvian Pacific drainage catchments

Abstract

Peruvian Pacific drainage catchments only benefit from 2% of the total national available freshwater while they concentrate almost 50% of the population of the country. This situation is likely to lead a severe water scarcity and also constitutes an obstacle to economic development. Catchment runoff fluctuations in response to climate variability and/or human activities can be reflected in extreme events, representing a serious concern (like floods, erosion, droughts) in the study area. To document this crucial issue for Peru, we present here an insightful analysis of the water quantity resource variability of this region, exploring the links between this variability and climate and/or anthropogenic pressure. We first present a detailed analysis of the hydroclimatologic variability at annual timescale and at basin scale over the 1970-2008 period. In addition to corroborating the influence of extreme El Niño events over precipitation and runoff in northern catchments, a mean warming of 0.2 °C per decade over all catchments was found. Also, higher values of temperature and potential and actual evapotranspiration were found over northern latitudes. We chose to apply the Budyko-Zhang framework that characterizes the water cycle as a function of climate only, allowing the identification of catchments with significant climatic and anthropogenic influence on water balance. The Budyko-Zhang methodology revealed that 11 out of 26 initial catchments are characterized by low water balance disparity related to minor climatic and anthropogenic influence. These 11 catchments were suitable for identifying catchments with contrasting change in their hydroclimatic behavior using the Budyko trajectories. Our analysis further reveals that six hydrological catchment responses can be characterized by high sensitivity to climate variability and land use changes.

Assessing multidecadal runoff (1970–2010) using regional hydrological modelling under data and water scarcity conditions in Peruvian Pacific catchments

“…The regional trend is mainly driven by northern and central catchments (no trend was obtained for the southern catchments plotted in Figure f). This can be explained by the effect of significant precipitation increase in northern region (Rau et al, ), as well as with the potential effect of snow and glacier melting due to increasing mean temperature around 0.2 °C per decade over the study area in the last four decades (Rau et al, ). The low values of annual modules for our unimpaired estimation is likely to be related with effects of water increase by the large hydraulic systems along the study area since the 1970s (Rau et al, ).…”

“…At an annual time step, according to Lavado et al () and Rau et al (), catchments in the study area generally follow a north–south gradient of decreasing mean annual precipitation and evapotranspiration as shown in Table .…”

“…In the same way, evapotranspiration reaches maximum values in the wet months from December to March. This could qualitatively explain the hysteresis effect mainly in the Piura (n°1) and San Juan (n°4) catchments, identified by Rau et al () as water‐balance‐sensitive to both precipitation and evapotranspiration. Finally, the main mechanism explaining the hysteresis effect is probably associated to a transient storage of water in a groundwater unit during the early wet season with increased flow during the whole wet season and early dry season.…”

“…A careful quality check of these data was previously performed. Monthly precipitation, temperature, and streamflow data were homogenized and validated according to Bourrel et al (); Rau et al (); Rau et al (). Precipitation and temperature data were interpolated to a 5 × 5 km grid using inverse distance weighting interpolation and considering altitudinal gradients.…”

“…More than 50% of the Peruvian population are situated within this region, which holds only 2% of all available freshwater in Peru (ANA, ). Previous studies, such as Lavado, Ronchail, Labat, Espinoza, and Guyot () and Rau et al (), showed evidence of poorly gauged and ungauged catchment conditions with strong anthropogenic influence (e.g., large hydraulic infrastructure) on water balance and runoff in the last four decades.…”