Mapping Annual Riparian Water Use Based on the Single-Satellite-Scene Approach

Abstract

Abstract:The accurate estimation of water use by groundwater-dependent riparian vegetation is of great importance to sustainable water resource management in arid/semi-arid regions. Remote sensing methods can be effective in this regard, as they capture the inherent spatial variability in riparian ecosystems. The single-satellite-scene (SSS) method uses a derivation of the Normalized Difference Vegetation Index (NDVI) from a single space-borne image during the peak growing season and minimal ground-based meteorological data to estimate the annual riparian water use on a distributed basis. This method was applied to a riparian ecosystem dominated by tamarisk along a section of the lower Colorado River in southern California. The results were compared against the estimates of a previously validated remotely sensed energy balance model for the year 2008 at two different spatial scales. A pixel-wide comparison showed good correlation (R 2 = 0.86), with a mean residual error of less than 104 mm·year −1 (18%). This error reduced to less than 95 mm·year −1 (15%) when larger areas were used in comparisons. In addition, the accuracy improved significantly when areas with no and low vegetation cover were excluded from the analysis. The SSS method was then applied to estimate the riparian water use for a 23-year period . The average annual water use over this period was 748 mm·year −1 for the entire study area, with large spatial variability depending on vegetation density. Comparisons with two independent water use estimates showed significant differences. The MODIS evapotranspiration product (MOD16) was 82% smaller, and the crop-coefficient approach employed by the US Bureau of Reclamation was 96% larger, than that from the SSS method on average.

Relationships between riparian evapotranspiration and groundwater depth along a semiarid irrigated river valley

“…Riparian water use continues to be an important area of research as large efforts are directed at controlling invasive riparian species (Bay & Sher, ; Khand et al, ) and competing sectors strain for already limited water availability. Tools that can provide accurate estimates of riparian ET at large spatial scales, such as SSEBop, can help inform water managers of the role of riparian consumptive water use.…”

“…Senay et al () applied SSEBop using 31 years of Landsat archives in the south‐western United States and found that annual median riparian and agricultural ET can range from 1,500 to about 2,000 mm/year. Khand et al () showed the use of a single satellite scene method, with NDVI as a key input, to have accurate comparisons with a sophisticated model over appropriate spatial scales and subsequently used the single satellite scene method to estimate annual riparian ET for 23 years. Their average annual water use on the Colorado River in southern California is 748 mm, which is 62% less than our simulated average for all years at 1,949 mm (e.g., Table ).…”

“…Previous studies have estimated remotely sensed riparian water use along the Colorado River (Glenn, Nagler, Morino, & Hultine, ; Khand, Taghvaeian, & Hassan‐Esfahani, ), the Rio Grande River (Nagler et al, ), the Verde River (Tillman, Wiele, & Pool, ), and the San Pedro River (Glenn, Scott, Nguyen, & Nagler, ), all of which supply water to irrigation districts with economic significance. The Arkansas River is an equally important water source that suffers from a similar non‐native species invasion of riparian ground but lacks a competing amount of ET estimates (Niemann, Lehman, Gates, Hallberg, & Elhaddad, ).…”

Effects of Distinguishing Vegetation Types on the Estimates of Remotely Sensed Evapotranspiration in Arid Regions

“…Accurate estimates of regional scale ET are needed for sustainable water resource management, particularly for arid ecosystems due to competing demands for water resources among agricultural irrigation, public and domestic needs, industrial production, and ecological environments [4,5]. In recent decades, some empirical remotely sensed ET models have been developed [6][7][8][9][10][11][12][13][14] and their potential for regional scale ET estimation in arid ecosystems has been demonstrated [15][16][17][18][19][20][21][22][23][24][25][26]. These models extrapolate ET observed or estimated at the site scale to regional scale based on the empirical relationship constructed at the local site scale, which relates daily ET from the eddy covariance or Bowen ratio flux towers to vegetation indices (VIs) and meteorological data [27][28][29].…”

A Modeling Framework for Deriving Daily Time Series of Evapotranspiration Maps Using a Surface Energy Balance Model

“…Numerous studies have demonstrated the use of time series ET maps for ecological applications, such as capturing the progress of vegetation and wetland restoration [18], assessing the vulnerability of forest to fire and drought [19] and accounting water use from riparian vegetation and invasive species [20][21][22][23]. Remote sensing-based ET products have also been applied in improving the performances of hydrological models [24][25][26] and for climate studies to capture water feedbacks associated with seasonal cycles and soil moisture deficit at regional scales [27].…”