A rapid and cost-effective method for vegetation mapping and nutrient content evaluation along the receding Lake Kinneret shoreline using oblique airborne video integrated into the GeoSky~(TM) system

摘要

Lake Kinneret is a major water source for the State of Israel, hence it is managed and preserved by the Israel Water Authority. Mapping the new vegetation growth along the exposed shores of Lake Kinneret during periods of retreating lake water levelsis of great importance in the management of the lake and its water quality. When the lake level rises this vegetation is covered by water, decays, and releases nutrients into the lake, possibly enhancing algal blooms. In December, 2001, when the lake level was -214.72 m, a rapid and cost-effective vegetation mapping was done along the retreating shoreline using a GeoSky~(TM) system that integrates oblique airborne video synchronized with Differential Global Positioning System (DGPS) and an electronic compass, and displays them within a Geographic Information System (GIS). Six major vegetation classes with twelve subclasses were interpreted from the video along the newly exposed shoreline between -209 m (highest lake level) and -214.72 m, their bordersmapped, and a total vegetation area of 73.6 km~2 was calculated. Dominant plant species, their features and structure were described. The coverage area of each vegetation class was mapped using the Arc View 3X (from ESRI) GIS tools within GeoSky~(TM), finding Phragmites australis, Tamarix sp., and Cyperus spg:as representatives of the major vegetation classes. The biomass of each major class was then calculated from the coverage area according to dry matter concentration of 2.5, 1.5, 1, and 0.5 kg/m2 ofPhragmites, Tamarix, Cyperus, and other, respectively. Total phosphorus (P) and total nitrogen (N) were calculated utilizing concentrations of 0.2% of total P and 1.2% of total N in the dry biomass of vegetation. Maximum cumulative inventories were evaluated to 23,500 kg of phosphorus and 141,000 kg of nitrogen. It was then recommended to the Water Authority of Israel to leave the shoreline vegetation untouched instead of cleaning it with a mower.