Evaluation in the Detection of Environmental Changes in the High Ipanema Watershed

Abstract The objective of this study was to identify and evaluate the different degrees of environmental susceptibility of the High Ipanema watershed, covering part of the municipalities of Arcoverde and Pesqueira in the state of Pernambuco, to climatic variability and degradation process. The data of monthly precipitation of the historical series (1962 to 2015) were used for the calculation of the rainfall anomaly index (IAC), considering the temporal means of the local precipitations, for the determination of dry and humid periods. The biophysical parameters were estimated for the detection of environmental changes in the watershed, applying components of the SEBAL algorithm using Landsat 5-TM and 8-OLI/TIRS images. The results presented a predominance of negative IACs for the interannual variability with more extreme inflection points in the rainy years, which shows the whole watershed with an anomaly index between dry and rainy. There is also strong evidence of the influence of the occurrence of El Niño and La Niña phenomena, together with or not on the positive and negative phases of the Atlantic Dipole, in the drought and rainfall events in the watershed. With the biophysical parameters analyzed it was found that the northwest part of the watershed presents a considerable area of exposed soils with a degree of susceptibility to degradation.

摘要 本研究旨在识别并评估覆盖巴西伯南布哥州（Pernambuco）阿科维德市（Arcoverde）与佩斯基拉市（Pesqueira）部分区域的伊帕内马高流域（High Ipanema watershed）对气候变异性与退化过程的不同程度环境敏感性。本研究采用1962年至2015年的历史月降水数据，以当地降水的时间平均值为基准计算降水异常指数（Rainfall Anomaly Index, IAC），以此确定干湿时期；随后通过应用SEBAL算法组件，利用Landsat 5-TM与8-OLI/TIRS影像估算生物物理参数，以检测流域内的环境变化。研究结果显示，流域年际变异性以负向降水异常指数为主，多雨年份存在更多极端拐点，表明整个流域的异常指数介于干旱与多雨状态之间；此外有充分证据表明，厄尔尼诺（El Niño）与拉尼娜（La Niña）现象的发生，无论是否与大西洋偶极子（Atlantic Dipole）的正负相位联动，均对该流域的干旱与降水事件存在显著影响。通过对所分析的生物物理参数进行研究发现，流域西北部存在大面积裸露土壤，其退化敏感性较高。