丹江口水库水质的遥感监测

丹江口水库作为南水北调中线工程的水源地,其水质安全将直接影响到调水工程的成败。根据丹江口库区2012年3月25日和8月9日的两幅HJ卫星遥感影像,结合同步的实测水质参数,采用经验反演模型对丹江口水库叶绿素a(Chl_a)浓度、总磷(TP)浓度和水体透明度(SD)进行了定量反演研究。结果显示,无论是枯水期和丰水期,丹库和汉库入库口的Chl_a浓度和TP浓度都要高于其他区域,而入库口区域的SD要低于其他区域。通过分析14项实测水质指标的主成分分析结果和丹江口库区LULC遥感解译结果发现,枯水期库区TP主要来源于库区上游城镇生活污水和工业废水,而丰水期TP主要来自于农业面源污染。SD反演结果还显示,由于汉江上游降雨量大,水土流失严重,使得汉库水体透明度明显低于丹库。利用Chl_a反演结果对丹江口水库的水体营养状态进行分析后发现,在丹库、汉库入库口区域以及水体流通性较小的狭小水体,水库水体达到了轻度富营养化状态,因此,应该加强对库区面源污染的控制和生态环境修复。

Remote Sensing Monitoring of Water Quality in the Danjiangkou Reservoir

Danjiangkou Reservoir is the water source area of the Middle Route of the South-to-North Water Transfer Project (MRSTNWTP). Thus, its water quality is of great significance to the project. In this study, we collected two HJ-1A/B remote sensing images of the Danjiangkou Reservoir in March and August, 2012. Combined with the in situ water quality data, retrieval models were established to analyze three water quality variables quantitatively, including the chlorophyll a (Chl_a) concentration, total phosphorus (TP) concentration, and water transparency (SD). The results showed that Chl_a and TP concentrations were much higher in the mouth of Dan region and Han region of the Danjiangkou Reservoir during both the dry and wet seasons, while SD was lower than that in other areas. Principal component analysis of the 14 water quality indicators and the remote sensing interpretation of LULC image in Danjiangkou Reservoir indicated that TP mainly comes from the domestic sewage and urban wastewater during the dry season, and from agriculture non-point source pollution during the wet season. The retrieval results of SD indicated that water loss and soil erosion in the upstream of Han River have negative effects on the water clarity of the Danjiangkou Reservoir, resulting in a lower SD in Han region than that in Dan region. Sediment deposition caused by soil erosion may decrease the storage capacity of the Danjiangkou Reservoir and endanger the safety of the MRSTNWTP. The retrieval results of Chl_a were used to analyze the water tropic status in Danjiangkou Reservoir, which indicated that Danjiangkou Reservoir was lightly eutrophicated in the mouth of the Dan region and Han region and some small water bodies. Thus, controlling the non-point source pollution in the upstream of Han River and ecological environment restoration should be implemented for water source conservation in the reservoir.