- 期刊
水里溪集水區檳榔種植對土壤沖蝕之影響及其經濟分析
Effects of Growing Betel Nuts on Soil Erosion from Shu-Li Creek Watershed and Its Economic Analysis
摘要
水里溪集水區位於台灣省中部，面積約7400公頃，內含三個水庫集水區及一個調整池。近年來，由於檳榔收益不斷提高，區內農民紛紛改種檳榔，大面積的改種使得生態環境改變，水庫涵養水源的功能降低；水土保持亦成為重要的課題。為瞭解水里溪集水區之土壤沖蝕之情形，本研究以修正土壤沖蝕模式（RUSLE）推估該集水區之土壤沖蝕量。模式之操作過程中，首先以地理資訊系統建立該集水區之環境資料庫，包含以5公尺為間距之等高線製作DEM，劃分子集水區；利用Kriging法推估未知的R值及K值分布圖。另外以Landsat TM衛星影像進行土地利用現況判釋，採用band3與band4之植生指數運算，作為集水區內之雜木林與檳榔園之判別；並以clay mineral指數運算，判釋非林地部分。本研究亦採用影像判釋結果，求得C值及P值。以GIS及影像分析技術，輔助土壤沖蝕因子之建立，使模式之推估更具效率。本研究所推估之沖蝕量，每一子集水區約在0.5-3.5公噸/公頃/年之間，但最高子集水區則達10.83公噸/公頃/年，該區檳榔種植面積佔85%以上。以整體集水區之水土保持治理經費觀之，該集水區之水土保持治理經費每年約1千6百萬元；在檳榔的益本分析方面，依本研究之計算，該集水區之年平均檳榔總收益約在9億元以上，與其每年治理之經費相較，在高收益高利潤的情況下，其治理經費之支出則易被忽略。
並列摘要
The Shu-Li Creek Watershed, having a total area of 7,400 hectares, is located in the center of Taiwan. In this watershed, three reservoirs, all one poundage for hydropower generation, and a tourist attraction site. The acreage of slopelands planted with betel nuts (Areca cathecu L. ) for higher economic return has expanded extensively in recent years. To perceive soil loss situation in this watershed, this research estimated soil loss by the Revised Universal Soil Loss Equation (RUSLE). An Integrated environmental database was established. Kriging method was used to interpolate the rainfall erosivity and soil erodibility factors (R and K) in RUSLE. Vegetation index and clay mineral index were employed to enhance Landsat TM images and identify land use pattern to obtain C and P factors. GIS and image processing technique is proven to be more efficient than conventional methods for model application. The estimated soil losses from each sub-watersheds range from 0.5 to 3.5 ton/ha/yr, with the highest one reached to 10.83 ton/ha/yr, where the betel nuts grown area occupied -, about 85% of the total sub-watershed. Moreover, the prevention and management cost of erosion was assessed. From benefit and cost analyes, an average of 900 million NT dollars net profit in betel nuts planting versus a 16 million NT dollars consumption in prevention and management cost was concluded. Apparently, under this comparison result, the prevention and management cost is easily neglected.