Low Altitude Unmanned Aerial Vehicles (UAVs) and Satellite Remote Sensing Are Used to Calculated River Discharge Attenuation Coefficients of Ungauged Catchments in Arid Desert

Abstract

The arid desert ecosystem is very fragile, and the change of its river discharge has a direct impact on irrigation and natural environment. River discharge attenuation coefficients is a key index to reveal the stability of desert river ecosystem. However, due to the harsh conditions in desert areas, it is difficult to establish a hydrological station to obtain data and calculate the attenuation coefficients, so it is urgent to develop new methods to master the attenuation coefficients of rivers. In this study, Taklamakan desert river was selected as the research area, and the river discharge of the desert river were estimated by combining low-altitude UAV and satellite remote sensing technology, so as to calculate the attenuation status of the river in its natural state. Combined with satellite remote sensing, the surface runoff in the desert reaches of the Hotan River from 1993 to 2017 were estimated. The results showed that the base of runoff attenuation in the lower reaches of the Hotan River is 40%. Coupled UAV and satellite remote sensing technology can provide technical support for the study of surface runoff in desert rivers within ungauged basins. Using UAV and satellite remote sensing can monitor surface runoff effectively providing important reference for river discharge monitoring in ungauged catchments.The attenuation coefficients of river discharge is the key index for maintaining fluvial ecosystems and arises through evaporation and infiltration during transport, which is usually calculated from the flow rate during the dry season [9,10]. The process of driving river attenuation depends on a series of physicochemical and biological parameters such as river velocity, temperature, vertical hydrological exchange of surface runoff and groundwater [11,12]. In the past 30 years, some relatively mature computational methods have been developed [13][14][15][16], which can be mainly divided into hydrological methods, hydraulic methods, habitat simulation methods and holistic analysis methods. These methods require a lot of information and require a long time of investigation, which tends to be carried out in areas with abundant hydrological data. However, large portions of total River Basins across the globe are either poorly gauged or completely ungauged [17][18][19], and hydrological observation networks are continuously deteriorating [20]. Therefore, there is a lack of research on surface runoff in ungauged catchments of arid desert [21][22][23], and the study on river attenuation is basically blank, resulting in high variability of attenuation rate in rivers, which complicates the prediction of environmental flows [24,25].Calculating the streamflow in ungauged catchments is surrounded by uncertainty, and is thus a challenging, yet vital task for water management. New and easily accessible satellite data have been increasingly steadily in recent years. Many studies have been conducted using satellite data to estimate river discharge [26][27][28]. Traditional methods for estimating river discharge mainly a...

Applications of Unmanned Aerial Systems (UASs) in Hydrology: A Review

“…Some authors propose the combined use of UAS with traditional hydrological formulas to calculate river discharge in ungauged areas. Yang et al [82] calculated the river discharge in ten sections in the Tibetan Plateau and Province of Xinjiang by (i) retrieving the parameters of the slope-area method using an UAS to generate a digital orthophoto map and a DSM and (ii) applying three different formulas (Manning-Strickler, Saint-Venant and Darcy-Weisbach). In Yang et al [83], UAS remote sensing, high altitude remote sensing and in situ measurements are combined to estimate river flow in medium/small wide shallow rivers in arid areas.…”

Simulation of Lake Water Volume in Ungauged Terminal Lake Basin Based on Multi-Source Remote Sensing

“…Riggs proposed the slope-area method (SAM), a classic hydraulic equation to calculate the runoff by using the slope and river cross-sectional area [38], that is based on physical laws and mathematical derivation and widely used for calculating the discharge of small-and medium-sized rivers [39,40]. We used three-dimensional surface data obtained from UAV-based remote sensing to calculate the river flow [41] with the SAM [42,43]. The equations used for the SAM calculation are as follows:…”

“…where v is the average flow, m/s; k is the conversion factor, m 1/3 /s (=1); n is the empirical roughness coefficient; the hydraulic radius R is the ratio of the river section area A to the wet cycle L; J is the hydraulic gradient of the river channel; and Q is the river flow, m 3 /s. The R and J values were obtained from UAV-based remote sensing [42,43].…”

Discharge Estimates for Ungauged Rivers Flowing over Complex High-Mountainous Regions based Solely on Remote Sensing-Derived Datasets

“…River flow monitoring with satellite remote sensing is an emerging discipline attractively increasing scientific interest [13,[19][20][21]. In terms of providing better spatial flow monitoring, this method is more appropriate than in-situ methods [6].Apart from the various hydrological modeling approaches, there is another more recent indirect methodology that uses Unmanned Aerial Vehicles (UAVs) to estimate water discharge by combining water level and velocity [22][23][24]. Moreover, river discharge can be also estimated using satellite radar altimetry of monitoring riverbeds [9,25], interferometric synthetic aperture radars (InSAR) [26,27], and passive microwave radiometers [28].…”

“…Apart from the various hydrological modeling approaches, there is another more recent indirect methodology that uses Unmanned Aerial Vehicles (UAVs) to estimate water discharge by combining water level and velocity [22][23][24]. Moreover, river discharge can be also estimated using satellite radar altimetry of monitoring riverbeds [9,25], interferometric synthetic aperture radars (InSAR) [26,27], and passive microwave radiometers [28].…”