Water quality monitoring in Mekong river basin in Laos
Monitored variables in the Mekong river basin in Laos are Escherichia coli concentrations and physico-chemical measurements in stream water. Physico-chemical measurements include water temperature, electrical conductance at 25 °C, dissolved oxygen concentration and saturation, pH, oxidation-reduction potential, turbidity, and suspended sediment concentration.
Details about the monitoring setup and the variables measured at multiple spatial scales in the Mekong river basin in Laos can be found here.
Hydro-meteorological and soil loss monitoring in Houay Pano catchment
Monitored variables in Houay Pano catchment are: 6-min and daily rainfall, hourly climate variables (wind speed, relative humidity, solar radiation, temperature), aperiodic water level, aperiodic suspended and bed particulate matter, and annual land use. At microplot scale, monitored variables are soil surface features, surface runoff, and soil loss.
Details about the monitoring setup and the variables measured in Houay Pano catchment can be found here.
In addition, groundwater in the Houay Pano catchment is monitored with automatic and manual piezometers, and through electrical resistivity tomography (ERT) survey.
Geometry of the weir at the S4 station, outlet of the Houay Pano catchment
Variables monitored in the Mekong nested catchments
| Variable (Unit) | Frequency | Method | Precision | Timeframe | ||
| Land Use | ||||||
| Spatial localisation | Yearly | Garmin GPS 12XL | 15 m | 1998–2005 | ||
| Garmin eTrex euro GPS | 10 m | 2006–2008 | ||||
| Garmin eTrex 10 GPS | 5 m | 2009–2015 | ||||
| Garmin GPSmap 60CSx | 3 m | Since 2016 | ||||
| Meteorology | ||||||
| Rainfall (mm) | Daily | 7 water level gauges (Homemade according to World Meteorological Organization standards) | 0.1 mm | Since 2001 | ||
| 6 min (Cimel) 1 min (Campbell) | Cimel ENERCO 407 (from 2001 to 2012); Campbell BWS200 with ARG100 – 0.2 mm capacity tipping-bucket (since 2013) | 0.5 mm (Cimel); 0.2 mm (Campbell) | ||||
| Air temperature (°C) | Hourly | 0.02°C (Cimel); 0.4°C (Campbell) | ||||
| Air relative humidity (%) | 0.5% (Cimel); 4% (Campbell) | |||||
| Wind speed (km h-1) | 10% (Cimel); 0.1 km/h (Campbell) | |||||
| Global radiation (J cm-2) | 0.05 J/cm2 (Cimel); 0.02 J/cm2 (Campbell) | |||||
| Soil surface features | ||||||
| Slope gradient | Flood event | 1-m2 microplot | 1 % | 2000-2016 | ||
| Areal % of free aggregates, free gravel, structural crust, erosion crust, gravel crust, charcoals, and residues | 5 %, 1 %, 5 %, 2 %, 2 %, 1 %, 5 % | |||||
| Areal % of worm casts and termite pellets, algae, mosses, crop and tree cover, weed and fallow cover at the soil surface | 1 %, 0.5 %, 0.5 %, 5 %, 5% | |||||
| Crop and tree height | 5 cm for crops, 200 cm for trees | |||||
| Weed and fallow height | 2 cm for weed, 20 cm for fallow | |||||
| Areal % of pedestal cover, pedestal maximum height, and pedestal mean height | 2 %, 0.5 cm, 0.5 cm | |||||
| Soil surface runoff and soil detachment | ||||||
| Surface runoff (mm) | Flood event | 1-m2 microplot | 5 mm | 2000-2016 | ||
| Soil detachment (g m-2) | 50 g m-2 | |||||
| Geophysics | ||||||
| Electrical resistivity tomography survey | 2003, 2005-2007, 2012, 2014-2015, 2024 | SYSCAL R2 (2003) and SYSCAL Pro (2005-2024) | 0.2 % | 2003-2024 | ||
| Electrical resistivity tomography time-lapse monitoring | Flood event up to 15-day time interval | SYSCAL R2 (2006-2007, 2010-2019) and SYSCAL Pro (2007-2010, 2019) | 0.2 % | 2006-2019 | ||
| Water and particulate transport at the station S4 (~1 km²) | ||||||
| Water level (cm) | 30 s | OTT Thalimedes | 0.1 cm | Since 2001 | ||
| Suspended particulate matter (g L-1) | Flood event | Automatic Pumping Type Sediment Sampler, ICRISAT | 0.01 g/L | |||
| Bed particulate matter (ton ha-1) | Monthly and/or flood event | Homemade concrete weirs | 0.001 ton/ha | |||
| Water quality at the 7 sampling stations (~1 to ~300,000 km²) | ||||||
| E. coli (MPN 100 mL-1) | 10 days | MUG/EC microplates on grab samples | Uncertainty is given by the Poisson law for each sample | Since 2011 or 2017 (Nou_1, Nse_1: 2017-2024) | ||
| Temperature (°C) | YSI 556-MPS (from 2011 to 2022); YSI Pro Quatro (since 2022) | ±0.15 C° (YSI 556-MPS); ±0.2 C° (YSI Pro Quatro) | ||||
| Electrical conductance (µS cm-1) at 25 °C | ±0.5 % | |||||
| Dissolved oxygen saturation (%) | ±2 % | |||||
| Dissolved oxygen concentration (mg L-1) | ±2 % | |||||
| pH (-) | ±0.2 | |||||
| Oxidation-reduction potential (mV) | ±20 mV | |||||
| Turbidity (NTU) | Portable turbidity meter (EUTECH Instruments TN-100) | ±2 % (0-500 NTU); ±3 % (501-1000 NTU) | ||||
| Suspended sediment concentration (g L-1) | Grab samples | |||||