Abstract
Baseflow estimation and evaluation are two critical and essential tasks for water quality and quantity, drought management, water supply, and groundwater protection. Observed baseflows are rarely available and are limited to focused pilot studies. In this study, an exhaustive evaluation of four different baseflow separation methods (HYSEP, WHAT, BFLOW, and PART) using surrogates of observed baseflows estimated with the conductivity mass balance (CMB) method is carried out using data from several streamflow gauging sites from the South Atlantic-Gulf (SAG) region comprised of nine states in the Southeastern U.S. Daily discharge data from 75 streamflow gauging sites for the period 1970–2013, located in the least anthropogenically affected basins in the SAG region were used to estimate the baseflow index (BFI), which quantifies the contribution of baseflow from streamflows. The focus of this study is to compare the four different baseflow separation methods and calibrate and validate these methods using CMB method based estimates of baseflows to evaluate the variation of BFI values derived from these methods. Results from the study suggest that the PART and HYSEP methods provide the highest and lowest average BFI values of 0.62 and 0.52, respectively. Similarities in BFI values estimated from these methods are noted based on a strong correlation between WHAT and BFLOW. The highest BFI values were found in April in the eastern, western, and central parts of the SAG region, and the highest contribution of baseflow to the streamflow was noted in October in the southern region. However, the lowest BFI values were noted in the month of September in all regions of SAG. The calibrated WHAT method using data from the CMB method provides the highest correlation as noted by the coefficient of determination. This study documents an exhaustive and comprehensive evaluation of baseflow separation methods in the SAG region, and results from this work can aid in the selection of the best method based on different metrics reported in this study. The use of the best method can aid in the short and long term management of low flows at a regional level that supports a sustainable aquatic environment and mitigates the effects of droughts effectively.
Highlights
Climate change and variability have been attributed to an increase in extreme hydrological events during the 21st Century in several research studies
The highest baseflow index (BFI) values were found in April in the eastern, western, and central parts of the South Atlantic-Gulf (SAG) region, and the highest contribution of baseflow to the streamflow was noted in October in the southern region
HYSEP [27], Web based Hydrograph Analysis Tool (WHAT) [39], BFLOW [32], and PART [36] baseflow separation methods were evaluated at several sites in the South Atlantic-Gulf (SAG)
Summary
Climate change and variability have been attributed to an increase in extreme hydrological events during the 21st Century in several research studies. Changes have been observed in sea levels to floods in different regions of the world. Nerem et al [1] detected that the global sea level had increased at a rate of 0.25 mm/year for 25 years, and this rate will continue to increase in the future. The climate change caused global river flood risk increased to 187%, but the flood frequency decreased in many agricultural and cropland areas [2]. Considering the European region, the frequency of river floods has increased with the peak discharges decreasing in Southern Europe and increasing in Central Europe [3]. Several major droughts have appeared in Texas (2011), the Amazon (2010), and Africa (2010), as noted
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