Hydroperiod maps of Donana for 2015/2016, 2016/2017 and their accompanying INSPIRE metadata XML files

The annual hydroperiod of wetlands, which is affected by global trends and human activities, is a critical ecological parameter that shapes aquatic plants’ and animals’ distribution and determines available habitat for many of the living organisms. Thus, its estimation is useful for the sustainable management of wetlands.

The hydroperiod maps for Donana are named: "Donana_Hydroperiod_from_1st_Sept_2015_to_31st_Aug_2016_using_Sentinel_2_and_Landsat_inundation_maps.tif" and "Donana_Hydroperiod_from_1st_Sept_2016_to_31st_Aug_2017_using_Sentinel_2_inundation_maps.tif". Their pixel values range from 0 to 365 (or 366 for leap years) and denote the number of days a pixel is inundated within a year. They were generated by interpolating satellite-derived inundation maps falling within the period indicated in their filenames.

The interpolation approach is the following: For two dates separated by n days, the occurrence of water is compared. If a pixel is inundated on both dates, then it is assumed inundated for n-days. If a pixel is not inundated on both dates, then it is assumed inundated for n/2 days. In the hydroperiod map, the total number of inundation days per pixel is determined by accumulating the inundated days throughout the desired time period.

湿地年度水文周期（hydroperiod）受全球变化趋势与人类活动共同影响，是调控水生动植物分布、决定诸多生物可利用栖息地的关键生态参数。因此，对其进行估算有助于湿地的可持续管理。

多纳纳（Donana）湿地的水文周期地图命名如下："Donana_Hydroperiod_from_1st_Sept_2015_to_31st_Aug_2016_using_Sentinel_2_and_Landsat_inundation_maps.tif" 与 "Donana_Hydroperiod_from_1st_Sept_2016_to_31st_Aug_2017_using_Sentinel_2_inundation_maps.tif"。其像素值取值范围为0至365（闰年为366），代表单个像素在一年内被水淹没的总天数。此类地图通过对文件名标注时段内的卫星反演淹没地图（inundation map）进行插值生成。

插值方法具体如下：以间隔n天的两个日期为基准，对比像素的水体覆盖状态。若某像素在两个日期均被水淹没，则认定其被淹没时长为n天；若两个日期均未被淹没，则认定其被淹没时长为n/2天。水文周期地图中单个像素的总淹没天数，通过累加目标时段内的各段淹没时长求和得到。