The Jason-2/OSTM satellite has now come to the end of its
primary 10-day repeat phase and has been moved to a new orbit. The last
cycle of data for Jason-2 will be cycle303 (September 2016). Data from
the Jason-3 mission (launched in January 2016) will now provide near
real time observations. There will be a short delay during October to
allow for new Jason-3 products to be created and merged with those from
Topex/Poseidon, Jason-1, and Jason-2.
The Jason-2 satellite will be moved to a new orbit at the end of September 2016. Near real time observation of water level variations will continue with the new Jason-3 satellite. There will be an interruption of weekly product updates during October while G-REALM transitions between the two missions.
June 6th 2016
Water level products for an additional 25 lakes/reservoirs were added to G-REALM in May:
0231.Saitlan (Russian Federation), 0425.Krasnoyarskoye (Russian Federation), 0434.Vilyuyskoye (Russian Federation), 0583.Bratskoye (Russian Federation), 0809.Votkinskoye (Russian Federation), 0810.Kamskoye (Russian Federation),
0900.Verkoneye (Russian Federation), 0948.Ondozero (Russian Federation), 1618.Nizhnekamsk (Russian Federation), 1341.Gorkovskoye (Russian Federation), 1376.Kuybyshevskoye (Russian Federation), 1378.Novosibirskoye (Russian Federation)
0355.Oulujarvi (Finland), 0358.Koitere (Finland),0397.Saimmaa (Finland),0401.Rijkavesi (Finland),0482.Mhisa (Norway)
- NORTH AMERICA
0003 Talbot (Canada), 0252.Cedar (Canada), 0254.Smallwood (Canada), 0380.Utikuma (Canada), 1155.Williston (Canada), 1240.GrandeRiviere_2 (Canada), 1372.Sipiwesk (Canada), 1490.GrandeRiviere_4 (Canada)
May 6th 2016
Water level products for an additional 33 lakes/reservoirs were added to G-REALM in April:
0349.Ziway (Ethiopia), 1436.Amboseli (Kenya), 0274.Kinkony (Madagascar), 0418.Faguibine (Mali), 0063.Rkiz (Mauritania), 1439.Shiroro (Nigeria), 1431.Sterkfontein (South Africa), 1458.Mtera (Tanzania)
1448.Karai (Iran), 0447.Hammar (Iraq), 0121.Pangong (India), 0519.Gandhi (India), 0958.Vallabh (India), 0625.Tarbela (Pakistan), 1503.Manchar (Pakistan), 0980.Noi (Thailand)
0320.Eyre (Australia), 0332.Torrens (Australia), 0758.Victoria_2 (Australia), 1440.Alexandrina (Australia), 1441.Albert(2) (Australia)
- CENTRAL AMERICA
0111.Ercek (Turkey), 1450.Karakaya (Turkey)
- SOUTH AMERICA
0345.Sobradinho (Brazil), 0422.Grazau (Brazil), 0448.Vermelha (Brazil), 0786.Araros (Brazil), 0804.Barragem (Brazil), 1419.Emborcacao (Brazil), 1422.Itumbiara (Brazil), 1554.Peixoto (Brazil), 1621.NovaPonte (Brazil)
October 8th 2015
- The surface water level variation products have recently been upgraded (from TPJO.1.1 to TPJO.1.3 and TPJO.2 to TPJO.2.3).
They have been re-calculated based on updated altimetric parameters and a revised reference datum.
End users are advised not to mix the old/new product versions.
- The upgraded TPJO.2.3 products now include correction factors in the ascii text file header
which will enable end users to translate the satellite-based time series into various
orthometric frames (approximating mean sea level). At the lake product level there is
also the option (left-hand panel) to view the reference and geoid height profiles which
were used to determine these correction factors. Details can be found in the Q&A link.
- Additional lake products displaying variations from 2008 to the present day at 10-day
resolution are also now available..
April 30th 2015 —
- The surface water level variation products have recently been upgraded (TPJO.3).
They have been re-calculated based on updated altimetric parameters and a revised reference datum.
End users are advised not to mix the TPJO.2/TPJO.3 product versions. Please discard the older products.
- The upgraded products now include two correction factors in the ascii text file header
which enable end users to translate the satellite-based time series to i) an orthometric
frame (approximating mean sea level) and ii) a WGS84 frame. At the lake product level
there is also the option (left-hand panel) to view the new reference datum for each lake,
and view the corresponding geoid profile. Details can be found in the Q&A link.
- Additional lake products at the 10-day resolution level and created with the NASA/CNES
Jason-2/OSTM mission data sets are also now available.
March 2nd, 2015 —
- Please note that the water level product for Lake Mosul
in Iraq (1534.Mosul) has recently been revised and now includes height
information for additional dates. Users are advised to only use the
variations displayed in this new product.
June, 2014 —
- The ENVISAT mission ended on May 9, 2012 and the ISRO/SARAL
mission is now recording lake level variations in the same 35-day repeat
cycle. The archive ENVISAT lake level products can now be found under
the 'One Click Options" above. New operational SARAL products are
expected to go on-line by early 2015.
January, 2013 —
- The lake level products derived from the NACA/CNES series of instruments (10-day temporal repeat) have been updated. The new JPJO.2 products are now available. Also note that the reference datum for each lake has now changed. It is no longer based on a 9-year mean level, but is based on full resolution (20Hz) data from a single fly-over date. In some cases the portion of the satellite track used over the lake has also changed to accommodate drought conditions. End-users should not mix the old TPJO.1 with the new TPJO.2.
April, 2012 —
- To aid users with converting the altimeter-derived relative time series of height variations into a series based on a mean sea level datum, additional products have now been made available. These new products are associated with the ENVISAT products and are in graph and text format. They show the geoid variation and lake reference datum across the lake. The lake reference datum is an elevation profile for a given date or satellite overpass cycle. The geoid profile has been constructed via interpolation of EGM2008. Details on how to use these reference datum and geoid profiles can be found in the FAQ section.
March, 2012 —
- 73 new ENVISAT lakes have been added and a total of 148 lakes are currently being monitored by ENVISAT.
March, 2012 —
- Users please note that a water-level product for the Kajakai reservoir is now available within the NASA/CNES series of satellite data. This product is Jason-2/OSTM only (i..e, post 2008) with a datum based on an individual (i.e., single-date) overpass within the OSTM timeframe. Based on a single overpass date (rather than 9year Topex mean datum) it therefore represents the start of the new TPJO.2 products which will emerge shortly and which will replace all existing TPJO.1 products.
January, 2012 —
- 18 new ENVISAT lakes have been added and a total of 75 lakes are currently being monitored by ENVISAT.
December, 2011 —
- 51 new ENVISAT lakes have been added and a total of 57 lakes are currently being monitored by ENVISAT.
October, 2011 —
- New ENVISAT products from the ESA satellite mission are in the process of being installed with 6 new lakes currently being monitored by ENVISAT.
January, 2011 —
- Users can now download all products at 1-click. See the option at the top left-hand side of this page. The 3 files are tar format and contain the text (raw and smoothed) and graphical products for all lakes currently in the database.
December, 2010 —
- An error in the surface elevation product for Lake Powell, USA has been identified and corrected this month. Users please note the new available time series is available for download.
August, 2010 —
TIME SERIES: The time series provided for each lake is not based on a fixed (lat/long) location but is derived from height information along a specific stretch of lake water. The location and extent of this stretch are in the ascii text files. As several lakes, reservoirs, and inland seas (e.g. Aral Sea, Guri reservoir) are experiencing drought or low-level conditions, the original lake stretch may now be including multiple pools of water each surface varying differently with time. This may lead to an erroneous overall mean measurement. In the future we may change the location of the stretch of water to minimize these problems but will announce such changes in the bulletins.
PRODUCT UPDATES: The lake products were modified in October 2009. Users should not mix the pre Oct 2009 product with the Nov 2009-2010 products as there are differences in reference datum and height corrections. Users should take the completely revised 1992-2010 product.
WEEKLY UPDATES: The time resolution of the NASA/OSTM products is 10-days but products are updated on a weekly basis if the satellite data is available to us. The last height value in the product text file may thus be set to 999.99 indicating that the available data was not yet available. Users should therefore check the height entries the following week to note the replacement of the 999.999 value with a valid measurement.
MISSING DATA: Note that the date/time/height parameters for Topex/Poseidon cycle118 and Jason-1 IGDR/cycle001 are all set to 999.999 default values. There was no lake data from these instruments during these periods.
SMOOTHED PRODUCTS: The format of the filtered/smoothed product text file has been altered. The date/time parameters are now set to the same format as the raw-data text file. Note that the filtered file 999.999 height entries reflect the original 999.999 values in the raw files i.e. the smoothing was not allowed to interpolate over original data gaps to avoid interpolation across too large a time period. The smoothed product file contains data that are sorted in mission order, not time order. The order of satellite mission is Topex, then Jason-1, then OSTM. There are 6month time periods when Topex/Jason and Jason/OSTM were flying in tandem, being only ~1minute apart on the same orbit. The data recorded by both instruments during these tandem periods will therefore overlap in time.
HEIGHT CORRECTIONS: The height of the lake is determined by applying a correction that takes into consideration the water vapor in the atmosphere. In cases where there is no such instrument-based or model-derived correction value, the water vapor correction field parameter (typically set to FMO=model or TMR=instrument) is now set to "N/A".
RADAR BACKSCATTER COEFFICIENT: The estimation of the radar backscatter coefficient (sigma0) value in the product text files, which can depict periods of calm or frozen water, has been revised. Typical values are in the range 10-50dB. Any 999.999 or 99.99 are default values and should be rejected.
October, 2009 — New time-series graphs for lake and reservoir water-levels measured by the Jason-2/OSTM satellite are now available. These new time-series graphs are preliminary and will be revised as the USDA/NASA GRLM project continues. The new time-series graphs have filenames called TPJO.1 (which stands for Topex/Poseidon/Jason/OSTM version 1). Users please note these TPJO.1 products also contain revised lake level estimates from the T/P and Jason-1 missions, i.e. there has been a revision of the old TPJ.2 products. See the reference section for details.
The Jason-2 or Ocean Surface Topography Mission (OSTM) was launched on June 20, 2008. It is the follow-on satellite to the Topex/Poseidon (1992-2002) and Jason-1 (2002-2008) missions, and continues the observations of surface water levels. The OSTM mission is a joint effort between NASA, CNES, NOAA and EUMETSAT with science objectives that focus on the ocean, as well as coastal and inland water regions. The new lake and reservoir water levels observed by the OSTM radar altimeter instrument will be continuously added to the existing time series on a weekly basis. Nevertheless, validation exercises, comparing TPJO.1 with ground based daily gauge data on the Great Lakes, USA are showing that the root mean square (rms) error on the current products are better than 10cm and this accuracy can be assumed for similar sized large lakes around the world.
Additional information on the Jason-2/OSTM mission can be found at:
August, 2009 — Data glitches delayed the release of updated graphs in June, but hopefully new graphs will be released in the next month or two.
March, 2009 — No Jason-1 product updates after January 2009 -- The lake level products in this data base have been derived from the NASA/CNES Topex/Poseidon (1992-2002) and Jason-1 (2002-2009) satellite missions. The Jason-1 mission reached the end of its nominal working phase at the beginning of 2009 and was shifted to a new orbit. Hence, there are no Jason-1 product updates after January 2009. However, the team are pleased to announce that the lake products will continue via data collected by the new Jason-2 (or OSTM) mission. In addition, many other lakes and reservoirs around the world are scheduled to be added to this data base via observations collected by the ESA ERS and ENVISAT missions. Look out for new OSTM products from April 2009 and new ERS/ENVISAT products towards the end of 2009.
August, 2007 — Jason-1 data modification --
Small modifications have recently been made to the lake level variations derived from the NASA/CNES Jason-1 mission. The update more accurately aligns the results of the Jason-1 mission to those of its predecessor Topex/Poseidon during the tandem phase (2002) and enables improved continuity from 2002 to the present day. Users are urged to utilize the revised Topex/Poseidon/Jason graphs and text files (TPJ.2 or Version 2) and to note that that new height offset between the missions (the 'relative bias') has been added to the header of the ascii text files.
August, 2007 — GFO data added --
Many of the lakes in the database are missing results derived from the Jason-1 mission. This is due to additional on-board and ground-based data filtering and out of the control of the reservoir project team. However, additional USDA and NASA funding is enabling the exploration of data from the US Navy's Geosat Follow On Mission (GFO). Preliminary GFO results are now provided here (TPJG.1 or Version 1) for a sub-set of the lakes. Users can access these results via clicking on the appropriate text next to the TPJ graphic products. Note that GFO samples each lake at a different location than Jason-1. Research continues to improve accuracy and consistency with respect to the NASA/CNES satellite data.