Derivation of Suspended Sediment Loads of Glacier-fed Andean Lakes, Reservoirs, and Rivers: Applications for Hazards and Water Quality

OBJECTIVES AND RELEVANCE: We propose to analyze NASA EMIT hyperspectral images and Landsat, Sentinel-2, and ASTER multispectral images to derive suspended sediment properties time series (abundance and grain-size distribution) and biological components in Andean glacier-fed natural lakes, reservoirs, and rivers in Chile and Perú. Our project responds to the 1st and 3rd HMA elements (1) research to assess and develop an early warning observable regarding regional geophysical hazards, and (3) impact decisions and actions through the application of hazards assessment to support local to national planning. A HiMAT-funded tool (GLAMBioLith-RT, part of GMELT, in GitHub) will be central in our analysis of NASA satellite imagery of Andean glacial waters. GLAMBioLith RT version 5 already is sufficient for needs, but we propose a set of fairly simple but very useful upgrades to version 6 that will improve output. Collaborators include basic and applied science specialists on Chilean glaciers and glacier-fed lakes and rivers.

METHODS: The quantitative analysis of EMIT data will be done using GLAMBioLith RT software developed for the High Mountain Asia team. The quantitative EMIT-based sediment properties then will be correlated with near-simultaneous (within 2 weeks) Landsat and ASTER image multispectral data to define confidence limits for multispectral-based sediment load estimations; then a 4-decade multispectral-based time series of relative changes in sediment properties of Andean glacial waters will be established.

The needed EMIT imagery covers most Andean glacial lakes, reservoirs, and large rivers in our regions of interest (Cordillera Blanca, Peru; Northern and Southern Patagonia icefields, Chile and Argentina). The time series will be examined for secular trends that are expected based on climate change and fluctuations of lake sizes.

VALIDATION: EMIT sediment properties derivations will be ground-truthed by analysis of dry-season water samples from four Chilean glacial lakes/large rivers for sediment grain size-frequency and mineralogy (suspended clastic sediment) and biology (phytoplankton and dissolved organic matter). The field collection of water from the lakes will be timed for an EMIT image acquisitions; imaging by Landsat 8 and 9, ASTER, Sentinel-2, and commercial PLANET also will acquired within a few days or a couple weeks of EMIT observations and the water collection.

BASIC SCIENCE: Turbidity times series for 65 (or more) lakes will be deconvolved for long-term trends (related to climate), annual oscillations (related to weather), and residual anomalies (some related to hazards). We must address the question: what is an unusual spike in turbidity, and how are such spikes connected with dynamical events that may be of alarming significance for early warning of potential hazard activity?

APPLIED SCIENCE: Applications science will be driven by a team of collaborators. The trip for field collection of water samples will also allow meetings with stakeholders and collaborators in Chile. The salient high-level study results will be provided to stakeholders and decision makers. The studies will include sedimentation of reservoirs, urban and rural water quality, and development of a concept for a turbidity-based data tool for lake hazard early warning. The early warning concept is that as a glacier undergoes sudden dynamic changes of potential hazard significance, hydrological changes may induce sediment spikes in glacier-fed lakes or rivers. A water quality application will include measurement by remote sensing of suspended sediment and estimation of riverine sediment flux. It is known from events in the Himalaya that water quality of glacier-fed rivers can reach extremely poor levels, necessitating the shut-down of water systems for cities as large as New Delhi, when landslide and avalanche activity affects glacier-fed river water supplies. Other applications will be oriented to estuarine and fjord ecosystems.