Continuous estimation of baseflow in snowmelt‐dominated streams and rivers in the Upper Colorado River Basin: A chemical hydrograph separation approach

Abstract

Effective science-based management of water resources in large basins requires a qualitative understanding of hydrologic conditions and quantitative measures of the various components of the water budget, including difficult to measure components such as baseflow discharge to streams. Using widely available discharge and continuously collected specific conductance (SC) data, we adapted and applied a long established chemical hydrograph separation approach to quantify daily and representative annual baseflow discharge at 14 streams and rivers at large spatial (> 1000 km 2 watersheds) and temporal (up to 37 years) scales in the Upper Colorado River Basin. On average, annual baseflow was 21-58% of annual stream discharge, 13-45% of discharge during snowmelt, and 40-86% of discharge during low-flow conditions. Results suggest that reservoirs may act to store baseflow discharged to the stream during snowmelt and release that baseflow during low-flow conditions, and that irrigation return flows may contribute to increases in fall baseflow in heavily irrigated watersheds. The chemical hydrograph separation approach, and associated conceptual model defined here provide a basis for the identification of land use, management, and climate effects on baseflow.

A new approach for continuous estimation of baseflow using discrete water quality data: Method description and comparison with baseflow estimates from two existing approaches

“…The objective of this study is to test the proposed approach by comparing the regression-derived baseflow estimates with CMB baseflow estimates calculated using measured high frequency SC data (assumed to be the most objective estimates of baseflow) at twelve snowmelt dominated streams and rivers in the Upper Colorado River Basin (UCRB). As previously reported by Miller et al (2014), CMB methods are well suited for estimating baseflow in snowmelt dominated watersheds. Baseflow estimates calculated using a commonly applied GHS model were also compared with measured CMB baseflow estimates.…”

“…1). Miller et al (2014) estimated baseflow discharge at a daily time step for the period of record at fourteen sites draining large watersheds in the UCRB characteristic of snowmelt dominated hydrology using measured high frequency SC data with a CMB approach. As part of this process sites were screened for impacts due to anthropogenic activities.…”

“…Average baseflow estimates range from 1.0 ± 1.2 m 3 /s to 103 ± 9.6 m 3 /s, and the fraction of total streamflow estimated to be baseflow ranges from 11% to 59% (Table 1). Detailed site descriptions for these twelve locations are available in Miller et al (2014).…”

“…Additionally, high frequency SC measurements can be obtained using in-situ SC probes. High frequency SC data and CMB methods have been used to estimate baseflow across gradients of watershed size and land use settings (Covino and McGlynn, 2007;Miller et al, 2014;Pellerin et al, 2007;Stewart et al, 2007).…”

The river as a chemostat: fresh perspectives on dissolved organic matter flowing down the river continuum

“…For example, the influence of groundwater discharge increases downstream (in other words, the dominance of one source over others), and this source of water may serve as a major control on the patterns of DOC concentration and DOM composition (e.g., Burgers et al 2014). There is also an increasing influence of stored water (i.e., lakes, reservoirs) downstream; these water stores are less dynamic in terms of DOC concentrations and they increasingly dominate river flow as basin area increases and therefore would contribute to the flattening (convergence) of C versus Q (Miller et al 2014).…”