Global 8-day/250-m surface water extent dynamics from 2000 to 2020 (GSWED250_2000-2020)

This product is designed to monitor the open surface water (called " surface water ") where the land surface is not blocked by vegetation and not frozen, including all types of water bodies such as rivers with a width greater than 250 meters and lakes and reservoirs with a surface area greater than 0.0625 Square kilometers. With the high temporal resolution (8-day), this product can be used to accurately reflect changes in the distribution of surface water over time (called “water dynamics“).
The product was generated based on the remote sensing vegetation index threshold method, in combination with multi-source remote sensing data (Han & Niu, 2020). The source data used to generate the product include MODIS-related data (MOD44W, MOD09Q1, MOD09A1, MOD13Q1, and MOD11A2) and topographic data (SRTM and GTOPO30).The GSWED was validated by using 8687 spatially and temporally random water samples, with an overall accuracy of 96%.
Land surface water dynamics is one of the most important indicators of changes in water resources. Accurate determination of land surface water dynamics is important for understanding the characteristics of the Earth system water cycle and its response to climate change and human activities. Such data products have important application values for water resources management.

本产品旨在监测地表无植被覆盖且未封冻的裸露地表地表水（open surface water，后文简称“地表水”），涵盖宽度大于250米的河流，以及表面积大于0.0625平方千米的湖泊、水库等各类水体。该产品具备高时间分辨率（8天），可精准反映地表水分布随时间的动态变化（water dynamics，后文简称“水体动态变化”）。
本产品基于遥感植被指数阈值法，并结合多源遥感数据生成（Han & Niu, 2020）。生成该产品的源数据包括MODIS相关数据（MOD44W、MOD09Q1、MOD09A1、MOD13Q1及MOD11A2）与地形数据（SRTM、GTOPO30）。本产品（GSWED）通过8687个时空随机水体样本开展验证，总体精度达96%。
地表水体动态变化是水资源变化的关键表征指标之一。精准监测地表水体动态变化，对于理解地球系统水循环特征及其对气候变化与人类活动的响应具有重要意义。此类数据产品在水资源管理领域具备重要应用价值。