Ecoregional Assessment of Biological Diversity in East Kalimantan

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East Kalimantan Ecoregional Assessment: Chapter 1 – Background & Analysis Process Major Rivers and Lakes Target Ecological Systems No standard, direct measure of the hydrologic condition of the Major Rivers themselves was available for this effort - at least not one that would enable a relatively objective comparison between any two rivers in the planning unit. Therefore, we developed a somewhat indirect assessment of functionality and condition of the rivers by ranking the condition of their surrounding vegetation coupled with flow contribution of their upper watersheds. In accordance with the zone recommended by the Indonesian Forests Department for large rivers (U.U. No. 41:1995), and by local experts on river sedimentation factors, the presence of healthy forests or other natural vegetation bordering rivers on both sides to a width of at least 500 meters is considered essential to the viability of rivers. Such a vegetation buffer reduces sedimentation and pollution loads into the river, shades and reduces water temperatures, protects its banks and physical environments for fish and other fauna, and supplements through litter-fall the nutrients in the river along various stages of its course. Therefore, viability for the major rivers was calculated on the basis of the condition of the forests that border three segments of a river, namely, 1) the Upper Catchment Area, 2) the Mid-stream Buffer Zone and 3) the terminal Delta area. Viability assessments for these three segments are described as follows: a. Upper Catchment Area Identified by aggregates of the sub-catchments that define the smallest upper catchment polygon that can be generated using ESRI Hydrological Modeling (Version 1), using 250 cells as a minimum input. Only catchment areas for the first order rivers that have a maximum flow accumulation value in the 1 st -2 nd standard deviation grouping as generated by ESRI were considered (Appendix III.A for an example). b. Midstream Buffer Zone Defined by a width of 500 meters on both sides of the stream. The values for mid-stream buffer zones were calculated by assessing the combined areas of the mid-stream buffer zones of the river branches that are fed by the upper catchments. Condition of these combined areas was calculated using the same approach as to estimate condition of vegetation inside an element occurrence (see terrestrial section above). c. Delta Areas The condition of the terrestrial target ecological systems of Mangrove Forest, Freshwater Swamp Forest and Peat Forest occurrences that are in contact with the Rivers at or near their terminal deltas (See Fig.2.C.1). These ecological systems have already been ranked prior to their selection and these same values are included in the overall rank for this section of the Major River target occurrence. 29
East Kalimantan Ecoregional Assessment: Chapter 1 – Background & Analysis Process Ranking condition of Upper Catchment areas, Mid Stream and Delta areas The condition of the three river segments was ranked in exactly the same way that condition was ranked inside an occurrence or for the landscape context of an occurrence (see subsection entitled Terrestrial Occurrences above. However, slightly different loading factors were applied (Table 1.3). Table 1.3. Reference table for values to apply to condition of the three segments involved in determining the viability index of the Major Rivers: River Part / Condition Very Good Good Poor Very Poor Upper Catchment 60 40 10 0 Midstream 30 20 5 0 Delta area 10 7 2 0 A complication arises when a river has more than one principal Upper Catchment area. In such cases, the values for the river were derived from a summation of the combined area of all its selected Upper Catchments. Each individual catchment polygon was ranked and multiplied by the proportion of the total combined area they represent to that river. The viability index for these rivers was achieved by clustering their accumulated rank values into statistical quartiles - and then using these quartiles to rank them as Very Good, Good, Poor and Very Poor. The following diagram illustrates the component rankings for a single river in Stratigraphic Unit 2 as an example. 30
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Ecoregional Assessment of Biological Diversity in East Kalimantan

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