Results

Parameters, frequencies, and the OLT data bases

Prepared by 

Xavier Lazzaro (HydroMet Buoy, sondes, weather stations, Information System)

Viviana Cruz Hernández (physico-chemistry, phytoplankton)

William Lanza Aguilar (periphyton on Totora stems, multi-variate analises)

& Javier Maldonado Alfaro (satellite remote-sensing of chlorophyll-a)

In progress; we are working on solutions to show the parameters evolution in real time from this webpage, as well as improve our data interpretations based on statistical and multivariate analysis

As part of the PNUD 05-B-05 Pilot Project we store all the databases generated into the IIGEO/UMSA GeoVisor platform (https://geovisor.umsa.bo), in the tabs 'Mi Boya' and 'Observatorio permanente del lago Titicaca' (https://miboya.geovisorumsa.com). It is divided into General Public, Researchers, and Managers. For now, it is in progress and only show a registration application form to be filled up. Our initial concept is that the General Public would have only access to the processed results presented as graphs, and their interpretations; whereas the researchers and managers, after being registered as authorized users, could request to access the databases. As we are only a small team of five people, we never had time to manage this complex manual procedure. Therefore, we rather decided that the users would register and request data directly from our webpage (https://olt.geovisorumsa.com). As we still don't have the budget to hire staff, the process remains manual. Just write to the Coordinator, Xavier Lazzaro, BOREA/IRD (xavier.lazzaro@ird.fr), and/or to the Deputy Coordinator, Javier Nuñez Villalba, IIGEO/UMSA (jnunezvillalba@gmail.com) who will send you two forms (registration, data request) to fill in, and to sign a commitment to cite the OLT observatory when their databases are used  in your publications. Being eligible, you will receive the requested data sets by e-mail. You will receive updates as time permit every 2-3 months, or more frequently upon requests. See the subpage <The Information System - Sharing Open Data>. 

The limnological stations databases

Within the included subpages, we show (campaign by campaign) the results of the surveyed 41 limnological stations on 37 sampling campaigns, ocasionnally from 2018 to 2021. Campaigns were performed at 1-2 week intervals in 4 zones of the Northern and Central regions of the Bolivian sector of Lago Menor. They were the basis of the OLT observatory to start understanding the spatio-temporal dynamics of the eutrophication process, prior to in situ validating the satellite remote-sensing estimates of chlorophyll-a concentration [Chl-a]. Depending on the probes used, the measured parameters were:

• The submersible multiparameter YSI EXO2 probe (the same as the one onboard the HydroMet buoy): Measures conductivity (µS/cm), temperature (ºC), pH and ORP (Oxydation Reduction Potential, mV), total chlorophyll-a and phycocyanin (RFU - Relative Fluorescence Unit), fDOM (fluorescent Dissolver Organic Matter, RFU), DO (Dissolved Oxygen, mg/L and % saturation), turbidity (NTU, Nephelometric unit), and depth (m). In addition, the EXO2 probe used in the campaigns is equiped with an EXO NitraLED, a UV Nitrate sensor (mg NO3.L-1). 

• The submersible flurorometer Moldaenke Fluroroprobe bbe: Measures the fluorescences of total chlorophyll-a, and 4 classes of phytoplankton microalgae: Greens (Chlorophytes), Cyanobacteria, Diatoms/Dinoflagellates (Bacillariophytes/Dinophytes), and Cryptophytes, both measured as µg/L (equivalent), and yellow substances (equivalent to CDOM). 

• The aerial and submersible spectroradiometer Biospherical C-OPS: Using 8 micro-radiometers, measures the solar energy received as ultarviolet radiations UV-B (305 and 313 nm), UV-A (320, 340, 380, 395 and 412 nm), and visible radiations (photosynthetic active or PAR: 412 nm and in the 400-700 nm). The single wavelengths are measured in µW.cm-1.nm-1, whereas the 400-700 nm range is measured in µE.m-2.s-1. These micro-radiometers equip both the aerial radiometer (Ed0) mounted on the top of a 3-m height pole on board the INTI boat, and the submersible radiometer (EdZ) mounted on a free fall mount (similar to a kite). Both radiometers are synchronized through the Deckbox and measure radiations down to 1 Hz frequency (1 measurement/s). The Ed0 measures the incident solar radiation, whereas the EdZ measures the downward radiation attenuated by the water column to calculate the extinction coefficient Kd and the extinction depth (z1%) of each wavelength (at which the radiation is only 1% of the surface radiation), from the equation: Iz = Io  * exp (- Kd *z), where Iz is the radiation at the z depth, and Io the subsuperficial radiation (underneath the surface). With Kd = -ln (0.01) / z1%. 

• The aerial spectroradiometer ASD FieldSpec HandHeld-2: Surface water reflectance in a 325-1075 nm wavelength range. Graphically displays the spectral signatures between wavelengths and reflectances (unitless). 

The HydroMet buoy meteorological databases

On board the HydroMet buoy, at the top of a 3-m pole an ultrasonic Vaisala weather transmitter WXT536 measures every 15 min the barometric pressure (mm Hg), air temperature (º C), relative humidity (%), wind speed (m/s) and direction (degrees), precipitation as rain (cumulative accumulation in mm between measurements, runs 1-min average in 10-s steps ) and hail (cumulative amount of hits against the collecting surface, counts each 10-s increment whenever hailstone detected, hits.cm-2). The file names of the meteo databases are in the form of: <Buoy_Met_IntervalData_ddmmyy initial date-ddmmyy final date_OLT_ok.csv>

The HydroMet Buoy water quality databases

The meteorological records and the water quality records are stored in separate Campbell CR1000 dataloggers. The data are collected by a router and remotely transmitted via cellular technology (ENTEL chip) in real time to the IIGEO/UMSA GeoVisor server, on the Cota Cota Campus, where databases are downloaded, validadted, analyzed, interpreted, and shared on the OLT observatory webpage. 

The LoggerNet program of Campbell generates two databases: one as 'surface' at 1-m depth with records every 30 min, and the other as 'vertical profile' between 1-m and 10-m depth (above the bottom) with records every one meter depth (1-min interval between depths) every 2 hours. At every depth, all the YSI EXO2 probe parameters are measured once:

• surface data (1-m depth): the file name has the form of: <Buoy_Profiler-PFL_Step_ddmmyy initial date-ddmmyy final date_OLT_ok.csv> 

• vertical profile data (1-10-m depths, every meter) : the file name has the form of: <Buoy_SondeHourly_ddmmyy initial date-ddmmyy final date_OLT_ok.csv> 

The Huatajata meteorological databases

The IRD/BOREA Huatajata Campbell weather station, installed by Xavier Lazzaro on the shore land of Maximo Catari Cahuaya in Huatajata, is registering data since 2012 until present (2024), with measurements every 15 min of the following average parameters: air temperature (AirTC Avg, º C), humidity (RH, %), solar radiation (400-1100 nm LiCor pyranometer, Rg_Avg, W.m-2, and SlrMJ_Tot, Mj.m-2), wind speed (WS_Avg, m.s-1), wind direction (WindDir, degre), rain (mm/5min), atmospheric pressure (BP_Avg, mbar), Photosynthetic Active radiation (LiCOR quantameter, 400-700 nm, PAR_Avg, W.m-2, and PAR_Avg, µmol.m-2.s-1). The file name has the form of: <Meteo_Huatajata_ddmmyy initial date-ddmmyy final date_OLT_ok.csv>. 

The satellite images

• Sentinel-2A-2B: images with 10-m spatial resolution, 5-day satellite pass, used to validate chlorophyll-a concentrations [Chl-a] from in situ measurements, after atmospheric correction, in order to assess phytoplankton biomass and the eutrophication state of Lago Menor. 

• Sentinel-3: images with 300-m spatial resolution, daily satellite pass, Optical Water Type (OWT)  GLaSS_6C classification of ESA used to map the lake trophic state.

• Landsat-2 to 8: NDVI (Normalized difference vegetation index) used to map the cover area of Totora emergent macrophytes in Lago Menor.

Both the databases and the satellite images are stored in the IIGEO/UMSA GeoVisor.