Abstract

SANABRIA SILES, Nelson Jery; SANDOVAL GOMEZ, María René  and  DALENCE MARTINIC, Javier Stephan. Downstream Influence Area of La Cañada Dam through Time Series of Spectral Vegetation Indices (Dry Period 1990 - 2022). RevActaNova. [online]. 2023, vol.11, n.2, pp.105-118.  Epub Nov 30, 2023. ISSN 1683-0789.  https://doi.org/10.35319/acta-nova.20233.

The construction of a dam that disrupts the water flow in a river can decrease both soil and leaf moisture in plants, or alternatively, it can positively alter the dynamics of vegetation along the riverbank. Vegetation can be estimated based on its reflectance using spectral indices. This study estimates the influence area on downstream vegetation of La Cañada Dam, utilizing time series of vegetation spectral indices during the low- flow period (June, July, and August), for purposes of delimitation of area of influence and monitoring. The presence of vegetation was evaluated using four spectral indices: NDVI, NDWI, MSI, and the Tasseled Cap greenness index; the latter index demonstrated a greater ability to accurately discriminate the presence of vegetation. Trend and homogeneity analyses reflect that prior to the construction of the dam, the data exhibited higher variability and a noticeable absence of vegetation; however, post-dam construction, a positive trend, and a significant increase in vegetation presence in the area are evident. It was demonstrated that the dam has a favorable impact downstream, with a 30% increase in vegetation areas and a 27,5% increase in greenness values indicating vegetation presence. 82 % of the area studied, presented a positive change in the presence of vegetation near the main river.

Keywords : Tasseled Cap; La Cañada; spectral indices; influence area; time series.

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