PERFORMANCE IMPROVEMENT AND DATA ASSIMILATION INTO CATCHMENT MODELS FOR THE EXPLOITATION OF RIVER AND LAKE PRODUCTS FROM ALTIMETRY

This proposal is made is response to RFQ ENVI-DTEX-EOPS-SW-07-0009. The pilot
system which produces river and lake heights from EnviSat Near Real Time (NRT)
altimeter data, has been running successfully for some time and has already attracted a
significant userbase. However, analysis of the system and outputs, together with research
progression since the design of the original system and significant user feedback, has
identified critical enhancements to increase the usefulness of these data, both in terms of
enhanced products from the EnviSat RA-2, and by increasing the system capability to
handle Jason-1 NRT data; this proposal addresses these issues.
The dissemination of these products and penetration of the ‘traditional’ hydrological
community can also be greatly enhanced using a two pronged approach: firstly, by
increasing the capability of the web based server and the associated outreach programme,
to ensure that potential users are made aware of these unique datasets and secondly, by
engaging directly with the hydrological community to address what is seen as the major
limitation of these data: the temporal sampling. Whilst for a large lake, crossed by
several tracks, the measurement temporal repeat will only be a few days, there is a
fundamental difference with river networks. Here, where the unique ability of the RA-2
to maintain lock on the underlying surface allows the measurement at multiple locations
along the earth’s major rivers, the temporal sampling of 35 days is perceived as a critical
constraint by the hydrological user community.
Experience with satellite oceanography suggests a remedy: incorporate these data into a
model, and thus integrate the measurements occurring at various locations along the river
system, either directly or as constraints on the model. In the developing world, where the
number of gauged catchments is continually falling and the rainfall measurements are
patchy at best, these data potentially provide a critical, and in many cases the only
possible information to monitor the earth’s surface inland water resources. However, the
very scarcity of rainfall data creates problems for hydrologists for whom this is the
primary key input. Accordingly, this proposal includes small studies from three groups
of river modellers, selected from the existing userbase of R&L data users. Each group
uses different hydrological modelling techniques and different proposed approaches, and
five river systems have been selected for this work, chosen as presenting a range of
different river types and geographical locations for which this approach is likely to be
viable. One river, the Mekong, is included from two groups, to assess the impact of
different hydrological approaches where the input altimeter data are identical for both.
It is proposed to publish the results of this work both on the River and Lake website and
as widely as possible at conferences and in the literature, to inform the wider
hydrological community of viable methods for including altimeter heights in their river
monitoring programmes, and stimulate a much wider market for these unique data.