实测与卫星观测德基水库水质变化

德基水库集水区的气候条件适合温带水果及高冷蔬菜、茶叶的种植,德基水库集水区上游遍布果园、菜园与茶园。因此,每逢大雨来临时,大量的残留肥料常遭冲刷至水库中。这些残留的肥料中含有大量的氮、磷等营养盐,足以提供水库微生物的生长繁殖所需,也因此造成水库中二角多甲藻的大量繁殖,进而形成藻华现象。研究使用Landsat TM卫星数据,搭配传统监测模式,以监督式影像分类法分析与监测德基水库1995年的藻华现象。研究结果显示,以Landsat TM卫星数据监测德基水库的藻华现象,其准确率可达87.5%以上。由影像分类的结果可得知,德基水库二角多甲藻之藻华现象发生较严重的时期为夏天,而冬天则较为轻微。此现象发生的原因,应与集水区上游的农业经营模式息息相关。此外,德基水库藻华现象发生的区域及其程度也经由实地调查与卫星影像监测,一一获得证实。

In-situ and satellite observations of water quality in the Techi Reservoir

The climate at the Techi Reservoir catchment is suitable for fruit,vegetable,and tea cultivation.So,there are many fruit,vegetable,and tea fields located in the upper stream of the Techi Reservoir catchment.The fertilizers applied are thus washed into the Techi Reservoir during heavy rains.These fertilizers contain vast amounts of nitrogen and phosphorous nutrients,which support the growth of dinoflagellate Peridinium bipes.The dinoflagellate Peridinium bipes cells increase rapidly and as a result Peridinium bipes algal blooms occur.Conventionally,large spatial scale algal bloom studies are conducted using boats and point sampling.This is expensive and time consuming.Remote sensing data can acquire temporal,large spatial,and vast spectrum data and also track the past data.Remote sensing,which quantitatively measures the light reflected from the surface of the earth,is a powerful tool for studying regional-scale aquatic ecosystem dynamics.In this study,Landsat TM data were used to monitor dinoflagellate blooms in the Techi Reservoir with supervised classification in 1995 and the predicted accuracies for algal blooms reached above 87.5%.From the classification results,dinoflagellate blooms were predicted most serious in summer and smallest in winter.The phenomenon was associated with catchment management.The catchments are located in the upper stream of the Techi Reservoir.The results afforded us the entire algal bloom information for the Techi Reservoir instead of the conventional point data.The algal bloom areas and degree of potential seriousness were defined in this study.