Estimating river discharge using multiple‐tide gauges distributed along a channel

Abstract

Reliable estimation of freshwater inflow to the ocean from large tidal rivers is vital for water resources management and climate analyses. Discharge gauging stations are typically located beyond the tidal intrusion reach, such that inputs and losses occurring closer to the ocean are not included. Here, we develop a method of estimating river discharge using multiple gauges and time‐dependent tidal statistics determined via wavelet analysis. The Multiple‐gauge Tidal Discharge Estimate (MTDE) method is developed using data from the Columbia River and Fraser River estuaries and calibrated against river discharge. Next, we evaluate the general applicability of MTDE by testing an idealized two‐dimensional numerical model, with a convergent cross‐sectional profile, for eighty‐one cases in which nondimensional numbers for friction, river flow, and convergence length scale are varied. The simulations suggest that MTDE is applicable to a variety of tidal systems. Model results and data analyses together suggest that MTDE works best with at least three gauges: a reference station near the river mouth, and two upstream gauges that respond strongly to distinct portions of the observed range of flow. The balance between tidal damping and amplifying factors determines the favorable location of the gauges. Compared to previous studies, the MTDE method improves the time resolution of estimates (from 2.5 to <1 week) and is applicable to systems with mixed diurnal/semidiurnal tides. However, model results suggest that tide‐induced residual flows such as the Stokes drift may still affect the accuracy of MTDE at seaward locations during periods of low river discharge.

Relative Sea Level, Tides, and Extreme Water Levels in Boston Harbor From 1825 to 2018

“…Therefore, the collapse of the M6 overtide in Boston Harbor likely reflects the greater average depth of the system caused both by channel deepening and by the significant loss of subtidal and intertidal habitat (Figure ). Interestingly, the M4 overtide slightly increased over time (Figure b), possibly indicating an increase in the (small) tidally averaged flow (e.g., river discharge or the return flow caused by tidal Stokes drift—see, e.g., Moftakhari et al, ) but also potentially caused by a decrease in damping of the overtide produced on the continental shelf (e.g., as occurs in the Ems Estuary; see Chernetsky et al, ). The divergence in the M4 and M6 overtide trends is an interesting challenge for a future numerical or analytical model to reproduce and explain.…”

Lateral variability of subtidal flow at the mid‐reaches of a macrotidal estuary

“…However, as river flow increases, there is a subsequent decrease in D6 generation [ Parker , ]. Alternately, a strong Stokes drift return flow could mimic river flow and produce D4 [ Moftakhari et al ., ]. To test whether this mechanism produced D4 in the Gironde, the Stokes drift transport was approximated in one dimension as (following Moftakhari et al .…”

“…To test whether this mechanism produced D4 in the Gironde, the Stokes drift transport was approximated in one dimension as (following Moftakhari et al . [] adapted from Longuet‐Higgins []). Here Q stokes is the Lagrangian Stokes drift, is the D2 tidal velocity amplitude, is the D2 tidal height amplitude, is the phase of the tidal velocity, and is the phase of the tidal height.…”

Development of the Stage Flow Relations for a Tropical Watershed

“…Various methods are available to estimate the discharge curve [9][10][11][12]. Since a continuous measurement of stream stage was obtained using the electronically recording level loggers, another method was available to obtain an estimate of the discharge curve.…”