An entropy‐based surface velocity method for estuarine discharge measurement

Abstract

An entropy-based method is developed to estimate estuarine river discharge from surface velocity measurements. A two-dimensional velocity profile based on the principle of maximum entropy is employed to express the mean velocity as a function of average surface velocity. The entropy-based flow profile is parameterized by the location of maximum velocity in the channel and the shape of the velocity distribution. The entropy parameters are quantified over the tidal cycle to account for the unsteady nature of estuarine flow. The method was tested using experiments conducted at the Danshui River, the largest estuarine system in Taiwan. Surface velocities were measured using an Automated River-Estuary Discharge Imaging System (AREDIS), and full-channel velocity profiles were measured with a moving-boat ADP survey. Entropy parameters were calibrated over the tidal cycle and linearly correlated with the average surface velocity to facilitate estimation from AREDIS measurements. The discharge calculated from average surface velocity and entropy relationships exhibits a 7.7% relative error compared to the ADP velocity profiles. The error nearly doubles when the mean values for entropy parameters are used instead of the variable parameters, indicating the importance of accounting for the unsteady nature of estuarine flows. Furthermore, the effects of measurement coverage area, types of entropy distribution, and wind-induced drift current on the surface velocity-based discharge measurement are evaluated and discussed. Overall, surface velocity measurements in conjunction with the entropy profiles well represent the flow in a complex estuarine environment to provide a reliable estimate of discharge.

Near-Field Remote Sensing of Surface Velocity and River Discharge Using Radars and the Probability Concept at 10 U.S. Geological Survey Streamgages

“…Subsequently, the record size was reduced from 7655 to 3099 samples. In general, model simulations can be considered satisfactory if the NSE exceeds 0.50 [93][94][95], PBIAS are within ±25% for streamflow [92][93][94], and VE approaches 1.0 [92][93][94]. The MAE and VE are most effective when used as an objective function for both low flows and high flows.…”

“…The location of the y-axis at Cherry Creek, Clear Creek, and the Tanana River was confirmed in the field using mechanical current meters or hydroacoustics. Previous investigations indicate the location of the y-axis is stable [66][67][68][69][70][71][72][73][74][75][76]95]; however, additional research is needed to corroborate the uncertainty of the shifts in the y-axis as a function of discharge. As such, research is being conducted on the Gunnison River, where video images are being collected and processed for PIV.…”

Estimating bankfull discharge and depth in ungauged estuaries

“…The river discharge is not only important for determining the salt intrusion, the potential for irrigation, or for ecological reasons, it is also important for understanding the morphology of estuaries. Recently, a new technology for estimating river discharge has become available using Horizontal Acoustic Doppler Current Profiler (H‐ADCP) [e.g., Bechle and Wu , ; Hoitink et al ., ; Sassi et al ., ]. However, this approach involves an extended period of repeated surveys which generally consumes considerable amount of time, energy, and money.…”

Development and Evaluation of Automatic Discharges Measurement Technology for Small Stream Monitoring

“…유량계측에 있어 필수적으로 요구되는 유속 측정방법은 하천규모, 접근성, 그리고 하천의 수리학적 특성에 따라 매우 다양한데, 프로펠러 유속계, 부자식 유속계 는 아직까지도 많이 사용되고 있는 방법이다 (Buchanan and Somers, 1969;Planchon et al, 2005;Leibundgut et al, 2009;Tazioli, 2011;Hrachowitz et al, 2013;deLima and Abrantes, 2014). 그러나 이들 유속계들은 (Fulton and Ostrowski, 2008;Alessandrini et al, 2013;Tarpanelli et al, 2013;Kim et al, 2015) (Fujita et al, 1998;Bradley et al, 2002;Creutin et al, 2003;Jodeau et al, 2008;Hauet et al, 2008;Hauet et al, 2009;Bechle et al, 2012;Gunawan et al, 2012;Bechle and Wu, 2014). 국내에서는 주로 실험수로 및 하천에서 표면 영상유속계를 검정하는 연구 (Yu et al, 2008;Choi et al, 2010) (Kim et al, 2008;Muste et al, 2011).…”