Predicting Climate Change Impacts on Water Balance Components of a Mountainous Watershed in the Northeastern USA

Abstract

Forcing watershed models with downscaled climate data to quantify future water regime changes can improve confidence in watershed planning. The Soil Water Assessment Tool (SWAT) was calibrated (R2 = 0.77, NSE = 0.76, and PBIAS = 7.1) and validated (R2 = 0.8, NSE = 0.78, and PBIAS = 8.8) using observed monthly streamflow in a representative mountainous watershed in the northeastern United States. Four downscaled global climate models (GCMs) under two Representative Concentration Pathways (RCP 4.5, RCP 8.5) were forced. Future periods were separated into three 20-year intervals: 2030s (2031–2050), 2050s (2051–2070), and 2070s (2071–2099), and compared to baseline conditions (1980–1999). Ensemble means of the four GCMs showed an increasing trend for precipitation with the highest average increase of 6.78% in 2070s under RCP 8.5. Evapotranspiration (ET) had increasing trends over the 21st century with the 2030s showing greater increases under both RCPs. Both streamflow (4.58–10.43%) and water yield (1.2–7.58%) showed increasing trends in the 2050s and 2070s under both RCPs. Seasonal increases in precipitation were predicted for most months of spring and summer. ET was predicted to increase from Spring to early Fall. Study results demonstrate the potential sensitivity of mountainous watersheds to future climate changes and the need for ongoing predictive modeling studies to advance forward looking mitigation decisions.

SWAT Model Performance Using Spatially Distributed Saturated Hydraulic Conductivity (Ksat) and Varying-Resolution DEMs

“…July is the wettest month, receiving an average monthly precipitation of 117 mm, while February is the driest month, with an average monthly precipitation of 66 mm [36]. On average, the West Run Watershed received a total annual precipitation of 1140 mm between 2001 and 2021 [38].…”

Impact of Climate Change on the Water Balance of the Akaki Catchment

“…Its latitude and longitude boundaries are 8°50′00″-9°10′00″ N and 38°35′00″-39°5′00″ E, respectively. The drainage area of the Akaki catchment is 1468 km 2 . The Little and Great Akaki watersheds are the main two sub-basins of the Akaki River and join together at the Aba-Samuel reservoir.…”

“…Concern about climate change has recently declined and has become a surprise issue for academic communities. Increased atmospheric carbon dioxide (CO 2 ) and associated greenhouse gas emissions are leading causes of warming trends, higher surface temperatures on Earth, and concurrent changes in precipitation regimes [2,3]. The rapid expansion of urban areas and the growth of industrial stages from time to time in various locations at the national and international levels have resulted in major disruption to the climate system due to the rising concertation of greenhouse gases.…”