Fig 1.
(a) Study Area (Sentinel-2 image 22/04/2018 - https://theia.cnes.fr/atdistrib/rocket/#/collections/SENTINEL2/8fb3429b-1ffc-53ff-bfb2-b5c75aba877f); (b) Zoom on the area of Dango, Dierma and Kapore; (c) Zoom on the area of Lengha, Lengha Peul, Yakala and Yakala Peul.
Fig 2.
Average monthly rainfall for the period 2000–2018 (bar chart in blue, Tenkodogo station), air temperatures for the period 2000–2018 (red line with dots, Fada N’Gourma station) and satellite-derived surface water temperatures for the period 2000–2018 (blue line with crosses).
Annual rainfall from 2000 to 2018 is shown in the inset (no data are available for 2001, 2003–2005 and 2010).
Fig 3.
(a) Ouazi Peul: example of site where water of the Bagre Reservoir is drawn for different domestic uses (drinking, cooking, washing, washing clothes), (b) livestock breeding at the Kapore routine site (2018/03/02), (c) “Puisard”.
Fig 4.
Temporal dynamics of E. coli and enterococci at the Kapore site (horizontal dotted lines correspond to USEPA 2012 bathing water quality standard: dotted lines in orange and blue show the limit for enterococci and E. coli, respectively).
Fig 5.
Enterococci vs E. coli for the Kapore routine point (N = 38), and for “puisards” (N = 6, yellow squares).
Table 1.
Correlation coefficients obtained by regressing E. coli and enterococci, and E. coli and environmental variables (N = 38 for enterococci, SPM, weekly and daily rainfall; N = 16 for cumulative rainfall; N = 22 for land NDVI, Sentinel-2 data; N = 19 for water pixels and water level).
Fig 6.
(a) Daily rainfall, (b) Weekly rainfall, (c) Cumulated weekly rainfall, (d) Number of water pixels from Sentinel-2 data, (e) Water level, (f) Average land NDVI from Sentinel-2 data, (g) Water NIR Reflectance (Sentinel-2), (h) SPM, (i) E. coli.
Fig 7.
Correlation circle of partial least squares (PLS) regression, illustrating relationships between predictor variables (blue), E. coli (orange) and the two first PLS components (first component on the x-axis, second one on the y-axis).
Fig 8.
Comparison of models’ predictions with observed E. coli (log values) (a) PLS model with all environmental variables and all components; (b) PLS model with NIR band, SPM and Weekly rainfall and all components; (c) PLS model with satellite variables only (NIR band and Weekly rainfall) and all components.
Fig 9.
Observed E. coli (black point) and predicted E. coli (green line for all variables, orange line for NIR band, SPM and Rainfall variables, blue line for satellite variables.
Fig 10.
Monthly incidence recorded in 2018–2019 and average recorded incidence for the period 2013–2018 for the 3 HPSC (Dango, Dierma, Lengha) and for all of these 3 HPSC (for January-March 2019 only the data of the HPSC of Dierma and Lengha were available).
Table 2.
Correlation coefficients obtained by regressing diarrhea incidence and E. coli, and diarrhea incidence and environmental variables over the period March 2018-March 2019.
Fig 11.
Monthly average of SPM (mg / l), E. coli (MPN / 100mL), NIR band (sr-1*1000) and land NDVI (* 1000), rainfall (mm), and cases of diarrhea for all 3 HPSC (Dierma, Lengha and Dango) over the period March 2018—March 2019.
Fig 12.
Correlation circle of partial least squares (PLS) regression, illustrating relationships between predictor variables (blue), cases of diarrhea (orange) and the two first PLS components (first component on the x-axis, second one on the y-axis).
Fig 13.
Comparison of models’ predictions with cases of diarrhea observed (a) PLS model with all environmental variables; (b) PLS model with Monthly rainfall, SPM, E. coli, NIR Band, and NDVI; (c) PLS model with NIR band, NDVI and Monthly rainfall.
Fig 14.
Observed diarrhea (black points) and predicted diarrhea cases using all variables (green line), NIR band, SPM, E.coli and rainfall variables (orange line) and only satellite variables (blue line).
Fig 15.
Evolution of the surface water area in the region of the routine measurement during the month of July 2018 (from left to right: Sentinel-2 images from 01/07/2018—https://theia.cnes.fr/atdistrib/rocket/#/collections/SENTINEL2/c0ff2b6e-1a94-5a31-b55f-c36f2b281d4c, 11/07/2018 - https://theia.cnes.fr/atdistrib/rocket/#/collections/SENTINEL2/fbbb8c73-7252-5310-80da-e2c2d9b4c4c4 and 31/07/2018 - https://theia.cnes.fr/atdistrib/rocket/#/collections/SENTINEL2/e787630e-5d67-5cc6-9eee-cdc668ef92f0).