Impact of Climate Change on Daily Streamflow and Its Extreme Values in Pacific Island Watersheds

Abstract

Abstract:The integration of hydrology and climate is important for understanding the present and future impact of climate on streamflow, which may cause frequent flooding, droughts, and shortage of water supply. In view of this, we assessed the impact of climate change on daily streamflow duration curves as well as extreme peak and low flow values. The objectives were to assess how climate change impacts watershed-wide streamflow and its extreme values and to provide an overview of the impacts of different climate change scenarios (Representative Concentration Pathways (RCP) 4.5 and 8.5) on streamflow and hydrological extremes when compared with the baseline values. We used the Soil and Water Assessment Tool (SWAT) model for daily streamflow and its extreme value modeling of two watersheds located on the Island of Oahu (Hawaii). Following successful calibration and validation of SWAT at three USGS flow gauging stations, we simulated the impact of climate change by the 2050s (2041-2070) and the 2080s (2071-2100). We used climate change perturbation factors and applied the factors to the historical time series data of 1980-2014. SWAT adequately reproduced observed daily streamflow with Nash-Sutcliffe Efficiency (NSE) values of greater than 0.5 and bracketed >80% of observed streamflow data at 95% model prediction uncertainty at all flow gauging stations, indicating the applicability of the model for future daily streamflow prediction. We found that while the considered climate change scenarios generally show considerable negative impacts on daily streamflow and its extreme values, the extreme peak flows are expected to increase by as much as 22% especially under the RCP 8.5 scenario. However, a consistent decrease in extreme low flows by as much as 60% compared to the baseline values is projected. Larger negative changes of low flows are expected in the upstream part of the watersheds where higher groundwater contributions are expected. Consequently, severe problems, such as frequent hydrological droughts (groundwater scarcity), reduction in agricultural crop productivity, and increase in drinking water demand, are significantly expected on Oahu. Furthermore, the extreme values are more sensitive to rainfall change in comparison to temperature and solar radiation changes. Overall, findings generally indicated that climate change impacts will be amplified by the end of this century and may cause earlier occurrence of hydrological droughts when compared to the current hydrological regime, suggesting water resources managers, ecosystem conservationists, and ecologists to implement mitigation measures to climate change in Hawaii and similar Islands.

Long‐term streamflow trends in Hawai'i and implications for native stream fauna

“…Shifts in rainfall will affect both groundwater recharge and streamflow patterns in Hawai'i (Leta, El‐Kadi, & Dulai, ). Statistical and dynamical downscaling of global climate model outputs indicate strong dipolar rainfall patterns, with greater contrast between windward and leeward areas due to increased orographic rainfall in windward areas and reduced rainfall in leeward areas (Elison Timm, Giambelluca, & Diaz, ; Lauer, Zhang, Elison Timm, Wang, & Hamilton, ; Zhang, Wang, Hamilton, & Lauer, ).…”

“…Vertical dike formations, that is, low-permeability volcanic intrusions, and perched aquifers maintain high-elevation groundwater that can contribute substantially to stream flows in deeply incised valleys (Lau & Mink, 2006). Shifts in rainfall will affect both groundwater recharge and streamflow patterns in Hawai'i (Leta, El-Kadi, & Dulai, 2018). Statistical and dynamical downscaling of global climate model outputs indicate strong dipolar rainfall patterns, with greater contrast between windward and leeward areas due to increased orographic rainfall in windward areas and reduced rainfall in leeward areas (Elison Timm, Lauer, Zhang, Elison Timm, Wang, & Hamilton, 2013;Zhang, Wang, Hamilton, & Lauer, 2016).…”

Assessment of the Impact of Climate Change on Daily Extreme Peak and Low Flows of Zenne Basin in Belgium

“…It has been well-documented that this climate change has already affected hydrologic cycle elements, such as precipitation, evapotranspiration, streamflow, soil moisture, groundwater recharge, and baseflow, including the response of rainfall-runoff processes [4][5][6]. Not only hydrologic cycle components, but also the magnitude, frequency, and timing of the occurrence of peak flows (floods) and low flows (droughts) have already been altered by climate change [4,5,[7][8][9][10][11][12]. Such impacts are expected to continue, and may result in adverse consequences on freshwater availability and sustainability, including frequent occurrence of hydrological extremes, such as flooding and droughts [4][5][6], which may have significant impact on riverine ecosystems and their natural habitats [13].…”

“…The advancements in GCMs coupled with several downscaling techniques for predicting future climate variables have led to increased confidence in the use of the GCMs' outputs. As a consequence, several researchers have used the locally downscaled climate change variables as direct inputs to basin-scale hydrological simulators and assessed the consequence of future climate change on river basin water balance components [4,6,18,[39][40][41], streamflow [7][8][9]42,43], and hydrological extremes [7,[10][11][12][13]16,27]. In Belgium, future changes in precipitation, temperature, and potential evapotranspiration (PET) have been predicted by using the CCI-HYDR perturbation tool [38,44], and their consequences on streamflow have been studied [27,28,[45][46][47].…”

“…In addition, a detailed overview on the possible impacts of climate change on the hydrological extremes of a spatially heterogeneous basin has not been reported yet. As the Zenne river basin experiences unique hydrologic features and complexity [48] and the impact of climate change is basin specific [8,12], investigating the implications of future climate change on hydrological extremes and better understanding these impacts are of major importance for the basin as well as its connected systems. Such studies can ultimately be used as an exploratory tool by water resources managers and decision makers to evaluate the consequences of future climate change on hydrological extremes of the basin.…”