Evaluation of climatic and hydroclimatic resources to support the US Army Corps of Engineers Regulatory Program

Abstract

Short-term climatic and hydrologic interactions, or hydroclimatology, are an important consideration when delineating the geographic extent of aquatic resources and assessing whether an aquatic resource is a jurisdictional water of the United States (WOTUS) and is therefore subject to the Clean Water Act (CWA). The now vacated 2020 Navigable Waters Protection Rule (NWPR) required the evaluation of precipitation and other hydroclimatic conditions to assess the jurisdictional status of an aquatic resource based on normal hydroclimatic conditions. Short-term hydroclimatic conditions, such as antecedent precipitation, evapotranspiration, wetland delineation, and streamflow duration assessments, provide information on an aquatic resource’s geo-graphic extent, hydrologic characteristics, and hydrologic connectivity with other aquatic resources. Here, researchers from the US Army Corps of Engineers, Engineer Research and Development Center (ERDC) evaluate tools and data available to practitioners for assessing short-term hydroclimatic conditions. The work highlights specific meteorological phenomena that are important to consider when assessing short-term hydroclimatic conditions that affect the geographic extent and hydrologic characteristics of an aquatic resource. The findings suggest that practitioners need access to data and tools that more holistically consider the impact of short-term antecedent hydroclimatology on the entire hydrologic cycle, rather than tools based solely on precipitation.

Case study of continental‐scale hydrologic modeling's ability to predict daily streamflow percentiles for regulatory application

“…Because Sparrow et al. (2022) found no evidence that the APT watershed analysis provides additional skill, when compared to an APT single‐point analysis, the APT watershed analysis was omitted in this study, and instead the study focused on the APT single‐point results.…”

“…However, Sparrow et al. (2022) screened the usefulness of the APT in determining streamflow normalcy and found that the APT's Antecedent Precipitation Score and the queried the National Oceanic and Atmospheric Administration (NOAA) Climate Divisional Database (nClimDiv) Palmer Drought Severity Index (PDSI) (NOAA, 2014) were not strong indicators of daily streamflow percentiles and were typically poor estimators of below normal, normal, and above normal streamflow conditions. Thus, there appears to be a gap in the available data for determining streamflow normalcy in ungaged streams.…”

“…The methodology within the APT has proven useful for evaluating precipitation normalcy for wetlands (Vepraskas et al, 2019). However, Sparrow et al (2022) screened the usefulness of the APT in determining streamflow normalcy and found that the APT's Antecedent Precipitation Score and the queried the National Oceanic and Atmospheric Administration (NOAA) Climate Divisional Database (nClimDiv) Palmer Drought Severity Index (PDSI) (NOAA, 2014) were not strong indicators of daily streamflow percentiles and were typically poor estimators of below normal, normal, and above normal streamflow conditions.…”

“…To perform the comparison, below normal, normal, and above normal categories were assigned to daily NWM21, GEO5, and USGS percentiles. Aligning with theSparrow et al (2022) study, the categories depicted in Table2were used to estimate below normal, normal, and above normal categories. The APT version 1.0.20 provided a similar categorization for its α in the form of the Antecedent Precipitation Condition and the monthly PDSI.…”

Antecedent Precipitation Tool (APT) Version 2.0 : technical and user guide

“…The user should consult multiple lines of evidence, in combination with APT, when analyzing the hydroclimatology of their observation point. Additional lines of evidence are cataloged and described by Sparrow et. al (2022).…”