CSIRO MD-WERP Maximum two-monthly surface water extent for MDB from MIM and WOFS - Version 2 SFA521

Data format: This product contains the maximum surface water extent across the MDB for each two-monthly period from 1988 to June 2022 (as observed from the MIM and WOfS data). This product consists of compressed GeoTIFF files, with a separate GeoTIFF for each two-monthly image. Each image is in WGS’84 geographic latitude/longitude projection (EPSG:4326) at a pixel size of 0.0002698 degrees (around 30 metres). There are three layers in this product: Surface water extent(‘WATER’), the algorithm used to classify each pixel (‘ALG’), and the image date used for each pixel in each two-monthly product (‘INDEX’). WATER: The surface water is provided using the following filename format: MIM_WOFS_V2_YYYY_MM_WATER_Mskd.tif Pixel values of ‘3’ represent water, ‘2’ represents dry, and ‘0’ represents null values. Null values can be areas which were cloudy, where there were no valid Landsat data, or areas of steep topography. A snow zone mask was also applied to the alpine region where snow often occurs and gets incorrectly identified as water. All pixels outside the MDB are masked as null values Maximum two-monthly surface water extent for MDB from MIM and WOFS – Version 2 Catherine Ticehurst, Dave Penton, Jin Teng, Ashmita Sengupta The multi-index method (MIM) (refer to Ticehurst, Teng and Sengupta 2022 for a description of the method) was developed for mapping surface water across the Murray-Darling Basin (MDB) based on Landsat surface reflectance data available in Digital Earth Australia. More than thirty years of two-monthly images of surface water extent across the whole MDB have been produced using this method, along with Water Observations from Space (WOfS) to help fill in gaps associated with cloud cover (due to the different cloud filtering methods used when reading in the data). The data were produced as part of the Murray Darling Basin Ecosystem Functions (MDB-EF) and Murray-Darling Water and Environment Research Program (MD-WERP) projects. This version of surface water extents was used to generate Version 3 of the FwDET water depth dataset. This version (Version 2) has the following improvements from Version 1: - The buffer around major perennial streams has been narrowed to better match the stream width. This was to reduce some of the noise identified within the river channel buffer during wet periods. - The WOfS (now known as Water Observations) product is from Digital Earth Australia Landsat Collection 3. Maximum two-monthly surface water extent has increased in many cases. However, some noise also appears in some images where WOfS has mapped water amongst clouds. The WOfS pixels can be identified using the algorithm layer (‘ALG’) within this product. - The Tasseled Cap Wetness index (TCW) has been refined such that TCW > –0.01 is used in ANAE riverine wetlands, and TCW > –0.035 is used in the remaining areas from Version 1. This was to help reduce over-estimation of water in some areas. - The workflow has been streamlined on EASI (Earth Analytics Science Innovation) platform for easy access to Landsat imagery via Open Data Cube and faster processing using AWS compute capacity https://doi.org/10.25919/s7c2-hc39数据格式：本产品涵盖1988年至2022年6月期间，墨累-达令盆地（Murray-Darling Basin, MDB）每双月周期的最大地表水范围数据，数据基于MIM与WOfS观测得到。本产品采用压缩GeoTIFF文件格式，每一期双月图像对应一个独立的GeoTIFF文件。所有图像采用WGS’84地理经纬度投影（EPSG:4326），像素分辨率为0.0002698度（约30米）。本产品包含三个图层：地表水范围（‘WATER’）、像素分类算法（‘ALG’），以及每一期双月产品中每个像素对应的成像日期（‘INDEX’）。 地表水范围（WATER）：其文件名格式为MIM_WOFS_V2_YYYY_MM_WATER_Mskd.tif。像素值‘3’代表水体，‘2’代表干地，‘0’代表空值。空值区域包括云覆盖区、无有效Landsat数据区或陡峭地形区。针对常发生积雪且易被误识别为水体的高山区域，已应用积雪掩膜。墨累-达令盆地以外的所有像素均被掩膜为空值。 《基于MIM与WOfS的墨累-达令盆地最大双月期地表水范围数据（版本2）》 作者：Catherine Ticehurst, Dave Penton, Jin Teng, Ashmita Sengupta 多指数法（Multi-index Method, MIM）（详见Ticehurst、Teng与Sengupta于2022年发表的方法描述）由研究团队开发，旨在基于澳大利亚数字地球平台提供的Landsat地表反射率数据，绘制墨累-达令盆地的地表水分布。团队利用该方法生成了覆盖整个MDB、时长超30年的双月期地表水范围数据，并结合空间水体观测（Water Observations from Space, WOfS）产品填补因云覆盖导致的数据空白（因数据读取时采用了不同的云过滤方法）。 本数据集是墨累-达令盆地生态系统功能（MDB-EF）与墨累-达令水体与环境研究计划（MD-WERP）项目的产出成果。本版本数据曾用于生成FwDET水深数据集的第3版。 相较于版本1，本版本（版本2）存在以下改进： 1. 缩小了常年大型河流周边的缓冲区，以更匹配实际河道宽度，旨在减少湿润期河道缓冲区中出现的部分噪声。 2. 本次使用的WOfS（现更名为空间水体观测）产品源自澳大利亚数字地球Landsat集合3。多数情况下，双月期最大地表水范围有所提升，但部分图像中因WOfS在云团中识别出水体，也引入了少量噪声。可通过本产品中的算法图层（‘ALG’）识别WOfS生成的像素。 3. 优化了缨帽湿度指数（Tasseled Cap Wetness, TCW）的阈值设置：在ANAE河道湿地中采用TCW > –0.01作为阈值，其余区域沿用版本1的TCW > –0.035阈值，以减少部分区域的水体过度估算问题。 4. 在EASI（地球分析科学创新，Earth Analytics Science Innovation）平台上优化了工作流，可通过开放数据立方体（Open Data Cube）便捷获取Landsat影像，并借助AWS计算资源实现更快的处理。 相关DOI：https://doi.org/10.25919/s7c2-hc39