datasciencecampus / sdg_661_analysis_and_reporting

Open-source tool for reporting SDG indicator 6.6.1

SDG 6.6.1 Analysis and Reporting

The Sustainable Development Goals (SDGs) have been developed by the United Nations as a “blueprint to achieve a better and more sustainable future for all”; designed to end poverty, halt climate change and reduce inequalities. The SDGs are made up of 17 goals and 244 indicators, making the mandate placed on all National Statistics Institutes to report on the SDGs a huge challenge.

This open-source tool looks to report on one of the 244 SDG indicators, 6.6.1:: Change in the extent of water-related ecosystems over time. The indicator focuses on water-related ecosystems that provide an important service to society, including open waters (rivers and estuaries, lakes and reservoirs), wetlands (peatland and reedbeds), and groundwater aquifers.

Data

⚠️ January 2022

At the time of creation versions 1.1 of the Monthly History and 1.2 of the Yearly history were used. The GSWE data are updated from time to time with version 1.3 of both datasets being the most current: Mothly History v1.3, Yearly History v1.3.

To accomodate any future changes the file gswe_versions.cfg can be updated with the corresponding asset IDs / URLs.

Here we use the Global Surface Water Explorer (GSWE) dataset developed by UN Environment Programme (UNEP), the European Commission Joint Research Council, and Google. GSWE is based on satellite imagery from the past 35 years. Currently GSWE measures changes in the distribution of inland open water e.g., lakes and reservoirs, a sub-indicator of 6.6.1.

GSWE is globaly and publicaly availabe, and can be extracted via the Google Earth Engine

GSWE data for the UK has already been extracted and can be accessed here

Extracting GSWE

Code has been developed to extract GSWE data to Google Drive using the GSWE_reporting package.

import ee
from GSWE_reporting import extract_gswe

ee.Authenticate()
ee.Initialize()  

geometry = ee.Geometry.Polygon( 
        [[[-12.598544729822379, 61.78863494939058],
          [-12.598544729822379, 49.00174346741333],
          [3.749111520177621, 49.00174346741333],
          [3.749111520177621, 61.78863494939058]]]) ## UK bounding box
         
# NOTE: Now using version 1.3 of the GSWE data
extract_gswe("JRC/GSW1_3/YearlyHistory", geometry, 1984, 2020, 'GSWE_exports')

Reprojecting GSWE

The GSWE is exported into WGS84 and when calculating water extent should be reprojected into a projected coordinate system

from GSWE_reporting import get_gswe_paths, reproject_GSWE

gswe_files = get_gswe_paths('./GSW_output/', '.tif')
reproject_GSWE(gsw_files, '+proj=utm +zone=30 +ellps=WGS84 +datum=WGS84 +units=m +no_defs ')

Preparing the boundary file

Water extent is aggregated to hydroBASINs (a series of polygon layers that depict watershed boundaries). They can be downloaded the HydroSHEDS page here. This is then clipped to a national boundary to ensure coastal waters are not included in reporting of inland waters.

from GSWE_reporting import clip_basin_to_boundary
hydrobasin_clipped = clip_basin_to_boundary(hydrobasin, boundary, target_crs)

Calculating Water Extent

With both the boundary and GSWE data processed, inland water extent can be calculated:

from GSWE_reporting import surface_water_extent

gsw_file_path_list = get_gswe_paths('./Reprojected/', 'UTM.tif')
hydro_basin = gpd.read_file('./boundaries/boundary.shp')
water_extent = surface_water_extent(gsw_file_path_list, hydro_basin)

UK Results

The results for the UK can be found in water_type_w_total.csv and water_extent_change.csv.

Water Extent

water_type_w_total.csv contains the spatial extent for each of the water types that can be derived from the Global Surface Water Explorer data (Permanent, Seasonal, and Ephemeral), aggregated to HydroBASINs from 1984 to 2019. It also contains the spatial extent expressed as a proportion of the HydroBASIN's area.

Columns
HYBAS_ID	Unique HydroBASIN ID
area	Area of the HydroBASIN (km2)
Year	Year of GSWE data
Ephemeral	Spatial extent of ephemeral water (km2)
Seasonal	Spatial extent of seasonal water (km2)
Permanent	Spatial extent of permanent water (km2)
% Ephemeral	Proportion of HydroBASIN area that is ephemeral water
% Seasonal	Proportion of HydroBASIN area that is seasonal water
% Permanent	Proportion of HydroBASIN area that is permanent water

Water Extent Change

As described by the indicators metadata, is calculated as:

where:
= the average national extent from 2001-2005
= the average national extent of any other 5-year period

The results for the UK can be found in water_extent_change.csv and describes the spatial extent change from the baseline to 2010-14 and 2015-2019.