Planet Action Landuse Changes around Riparian Zones Lake Atitlan, Guatemala November 10, 2011
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Planet Action Lake Atitlan Landuse Changes Date: November 8, 2011 Submitted online to Planet Action.org Submitted by: Luis Ivan Girón, Josie Thompson, Mateo Queché Intro The Atitlan Basin is almost entirely located in the Department of Sololá (1.142 sq km). There are 19 municipalities in the Department of Sololá and 13 of them overlap with Atitlan Basin. The entire extent of the Atitlan basin is 541 sq km, equal to the size of X. The majority of the population is Maya: only about 5% are Ladinos, except in Panajachel, which in recent years has seen an increase of both Ladinos and foreigners. The natives mainly speak the native Maya languages: Kachiquel and Tu’zutuil.
Ilustración 2: Department of Solola & Atitlan Watershed
Much of the Maya culture remains intact Map 1: Atitlan Basin's location in the Department of Solola in the villages. The natives are skill farmers, at times cultivating remote plots. They grow corn, coffee, beans, onions, potatoes, oranges, avocados, “pitayas” and bananas. They also grow flowers, “maguey” and tule (cactae). Weaving has for centuries been important among these people, even if over time their clothing has changes in color and design. While many traditions remain intact, others are slowly disappearing under the impact of the modern world. As part of a Planet Action Grant (8941), Vivamos Mejor and Accumaps have received seven Spot Imagery Scenes, ArcInfo & ENVI Software Licenses to analyze landscape changes between the years (2004, 2008, 2011) Five of the SPOT Imagery scenes cover the extent of the Lake Atitlan Watershed and were chosen to depict three distinct years that correspond with the last two major hurricanes and tropical storms (Stan ’05 & Agatha ’09). Map (3) shows on of the three years (2008). Notice that the northern portion of the watershed has the most land utilized as of settlement and agricultural use. With this information and new software, our team set out to define the landscape changes between these time periods and identify the clandestine garbage dumps. Map 2 : Sololá & Atitlan Basin upclose
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ENVI Methods As part of the Planet Action Grant (8941), a ENVI, a remote sensing software package was installed and the objective was to analyze the vegetation changes with ENVI’s Vegetation Index Calculator: Normalized Difference Vegetation Index (NDVI) Analysis was successful at separating out the general four classes of vegetation and helping us to distinguish between urban or agricultural base land from forest land. We used the NDVI to transform the three sets of SPOT multispectral data into a single image band representing vegetation distribution. The NDVI (Normalized Difference Vegetation Index) values indicate the amount of green vegetation present in the pixel. Higher NDVI values indicate more green vegetation. Map 3: 2008 Spot Imagery
ENVI’s NDVI uses the standard algorithm: Valid results fall between -1 and +1. ENVI has pre-set bands for AVHRR, Landsat MSS, Landsat TM, SPOT, or AVIRIS data or you can enter the bands to use for other data types. The three spot images were reclassified as forest, non-forest and calculated using map calculator in ArcINFO to determine where the landscape had changed over the six year period. Three categories: 1. No Change Urban 2. Changed 3. No Change Forest
Map 5 NDVI Analysis of Lake (5 categories)
Map 4 Reclass into three categories
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ArcGIS 10 Methods After analyzing the Landuse changes from 2005 – 2011 and the reclassed maps, Nine zones were identified as critical for riparian improvement based off of a 200 meter buffer and temporal analysis with SPOT Imagery (See Map 5). The criteria for selecting these areas were: 1. 2. 3. 4.
Deforestation Confluence of streams/rivers Size of Area Health of Riparian Zone
Atitlan Basin is considered a high risk area due to the heavy annual rains. In several locations there are gravel quarries in the stream bed causing major runoff. Upstream settlement oftentimes extend to the edge of the river, not leaving any riparian zone. This over use of the terrain has led to many landslides resulting in large public relief efforts and expenses, most recently October, 2011.
Map 5: Nine Critical Zone and Reclassed Ripiarian Zones with 200 Meter Buffer
Although the lake looks “green” when one is in the middle of the lake, what they don’t see is the extensive community to the north whos agricultural runoff and settlement patterns greatly effect the water quality of the lake. In this case, the viewshed is greatly incongruent with the watershed. Huge amounts of sediment stream down principally four rivers into the watershed. (Quiscab, Buenaventura, Cojolyá, Panajachel)
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Critical Areas Up Close:
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Critical Areas
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What did not work The imagery had a lot of clouds so a few of the areas were misinterpreted due to shadows or a lack of light. Our main concern was the riparian zone since the Lake is experiencing very high volumes of sedimentation, continuously into the lake, including agricultural runoff and many clandestine garbage sites (>1,600). Out thought that focusing on the riparian zone would aid us in finding critical areas to focus on for re-vegetation of ground cover and protection of the waterways. As part of the Planet Action Grant (8941), a ENVI, a remote sensing software package was installed and the objective was to analyze the vegetation changes with ENVI’s Vegetation Index Calculator: However, when we opened the DIMAP information for the external SPOT imagery data source, the error “no external band combinations could be found” so we could NOT use the vegetation analysis tools. Instead, we used NDVI analysis to separate out the changes in vegetation. Conclusion It is recommended that the communities are educated in 2012 about the effects of deforestation, especially around the riparian zone has on the lake and a comprehensive watershed plan is developed for each of the communities.
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Thank for the support from:
Patricia Dankha, Account Manager Planet Action (France)
SPOT Production Operators, ASTRIUM Geo-Information Services
Joel Griebel, Technical Support Analyst, Mari P. Minari Support Engineer
Alexander Yumakaev, ESRI Conservation Program Coordinator, Luis Fernandez, Principal (Geosistec)
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