Abstract
AbstractFrequent and continuous water quality monitoring of Olushandja Dam in Namibia is needed to inform timely decision making. This study was carried out from November 2014 to June 2015 with Landsat 8 reflectance values and field measured water quality data that were used to develop regression-analysis-based retrieval algorithms. Water quality parameters considered included turbidity, total suspended solids (TSS), nitrates, ammonia, total nitrogen (TN), total phosphorus (TP) and total algae counts. Results show that turbidity levels exceeded the recommended limits for raw water for potable water treatment while TN and TP values are within acceptable values. Turbidity, TN, and TP and total algae count showed a medium to strong positive linear relationship between Landsat predicted and measured water quality data while TSS showed a weak linear relationship. The regression coefficients between predicted and measured values were: turbidity (R2 = 0.767); TN (R2 = 0.798,); TP (R2 = 0.907); TSS (R2 = 0.284,) and total algae count (R2 = 0.851). Prediction algorithms are generally the best fit to derive water quality parameters. Remote sensing is recommended for frequent and continuous monitoring of Olushandja Dam as it has the ability to provide rapid information on the spatio-temporal variability of surface water quality.
Highlights
Fresh water is a finite resource that is essential for human existence (Bhuyar et al a, b; Bhuyar et al )
The mean field measured water quality parameter data acquired from four sampling campaigns (26 Feb–15 April 2015) were calculated at each of the six points
This study proves that medium resolution images such as those of Landsat are able to predict water quality parameters based on high regression coefficients (>0.75), as observed in studies by Concha & Schott ( ), Chen & Quan ( ), He et al ( ) and Hellweger et al ( )
Summary
Fresh water is a finite resource that is essential for human existence (Bhuyar et al a, b; Bhuyar et al ). Without freshwater of adequate quantity and quality, sustainable development will not be possible (UN-Water ; McMillan et al ). Effective management of this scarce resource ensures that present generations’ needs do not deprive future generations the same privileges of access in both quantity and quality as envisioned in the Sustainable Development Goals (SDGs) (Bain et al ). Man-made reservoirs such as dams and lakes are threatened by nutrient enrichment and heavy metals and their water quality is continuously degraded as a result (Oberholster & Ashton ; Nhapi ; Lehmann ). The water quality in Von Bach and Swakoppoort Dam in the Central Area of Namibia has been reported to be poor due to treated and at times partially treated wastewater from the City of Windhoek and Okahandja town (Lehmann ; NamWater )
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