Water Quality Assessment by Measuring and Using Landsat 7 ETM+ Images for the Current and Previous Trend Perspective: Lake Tana Ethiopia

Moges, Mamaru A.; Schmitter, Petra; Tilahun, Seifu A.; Ayana, Essays K.; Ketema, Atikilt Abebe; Nigussie, Temsgen E.; Steenhuis, Tammo S.

doi:10.4236/jwarp.2017.912099

Cited by 27 publications

(26 citation statements)

References 36 publications

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“…The available phosphorus concentrations in the lake bottom sediments were not related to any other measured parameter ( Table 1), indicating that the conversion processes that caused the pattern are unique. We should note that Gumara and Rib rivers that enter the lake on the east side have during the rainy season a dissolved P concentration that exceeds the lake concentration [27,30,47,66]. In the Awramba watershed close to lake outlet, the concentration was about three to four times the observed average dissolved phosphorus content in the lake of 0.18 mg L −1 [26,66].…”

Section: Discussionmentioning

confidence: 80%

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Bottom Sediment Characteristics of a Tropical Lake: Lake Tana, Ethiopia

et al. 2020

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Sediment concentration of rivers in developing countries has been increasing greatly over the last 50 years due to the conversion of forest to continuously cultivated land with the increasing population. Few studies have addressed its effect on sedimentation and water quality of the lakes by analyzing bottom sediment characteristics. In this study, the objective was to investigate the spatial distribution (and their interrelationships) of the bottom sediment characteristics in the largest lake in Ethiopia, Lake Tana where water hyacinths have been spreading rapidly during the last decade. Sediment samples were collected from the lake bottom at 60 locations and analyzed for texture, organic matter, total nitrogen, and available phosphorus. Bottom sediment samples had a median of 75% clay, 13% silt, and 9% sand. Clay was greatest in the northwestern part and smallest in the areas near the major rivers entering or exiting the lake. Clay percentage and lake depth were strongly correlated. The mean organic matter content of bottom sediment was 16 g kg−1, total nitrogen 0.8 g kg−1, and Olsen available phosphorus 19 mg kg−1. Phosphorus concentrations peaked where water hyacinths were found in the northeastern part of the lake. This study will serve as a baseline for future water quality and sedimentation changes in Lake Tana. In particular, it might aid in explaining the spread of the water hyacinths.

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Section: Discussionmentioning

confidence: 80%

“…In addition, the nutrient input from the upland agricultural areas has increased [26,46]. Phosphorus concentrations in the lake water have been rising [47] and have resulted in a progressive change of the lake from mesotrophic to eutrophic status [31].…”

Section: Study Areamentioning

confidence: 99%

Bottom Sediment Characteristics of a Tropical Lake: Lake Tana, Ethiopia

et al. 2020

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“…ese conventional methods are more precise, but they are carried out with limited water samples over space and time, thus may not reflect the overall lake water quality [4]. ey are not only limited in their spatial and temporal coverage but also timeconsuming and expensive [4][5][6][7][8][9]. In this paper, site-specific relationships are developed for mapping suspended sediment concentration (SSC), turbidity, and Secchi disc depth on Lake Tana.…”

Section: Introductionmentioning

confidence: 99%

“…Over recent decades, a number of studies have demonstrated that suspended matter distribution in inland waters can be mapped from various types of satellite remote sensing data, such as Landsat TM, Landsat ETM+, and Landsat-8, Moderate Resolution Imaging Spectroradiometer (MODIS), Medium Resolution Imaging Spectrometer (MERIS), Advanced Very High-Resolution Radiometer (AVHRR), Sea-Viewing Wide Field-of-view Sensor (SeaWiFS), and Satellite Pour I'Observation de la Terre (SPOT) [4][5][6][7][8][9]11]. Previous studies have proposed Landsat-7 ETM+ and Landsat-8 bands as a spectral self-phase modulation (SPM), turbidity, and Secchi disc depth (SDD) indicator for Lake Tana [5,8], but its limitation on the temporal resolution is insufficient for the study of dynamic changes of sediment. Kaba et al [7] used Terra-MODIS to investigate the relationship between water quality parameters and Terra-MODIS derived reflectance only at Gumara river inlet to Lake Tana.…”

Section: Introductionmentioning

confidence: 99%

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Estimation of Suspended Sediment Concentration from Remote Sensing and In Situ Measurement over Lake Tana, Ethiopia

Womber¹,

Zimale²,

Kebedew³

et al. 2021

Advances in Civil Engineering

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Discharge from basins joining a lake is the main factor determining the lake volume and sediment inflow to the lake. Suspended sediment is an important parameter for describing the water quality of aquatic ecosystems. Lake Tana is an important and the largest lake in Ethiopia for the local ecological system. However, environmental change and anthropogenic activities in the area threaten its water quality. The conventional methods of suspended sediment concentration (SSC) observation are unable to determine and compare spatial and temporal SSC patterns for the lake over a period of years. Remote sensing methods have made it possible to map SSC. The objective of this study is to characterize the spatial and temporal distribution of suspended sediment of Lake Tana using in situ measurement and remote sensing applications and specifically to develop a relationship between in situ and remote sensing observation to retrieve suspended sediment concentration and map the spatal distribution of SSC. This study used MODIS-Terra and in situ data to characterize the spatial and temporal distribution of SSC in the rainy season. Four sampling campaigns (20 samples per campaign) were carried out on Lake Tana, and the first three sampled campaigns on May 11–13, 2018, June 08–10, 2018, and July 15–17, 2018, were used for calibration of regression models. MODIS-Terra reflectance in NIR was found best related to in situ water quality data and varies linearly with SSC (r2 = 0.81) and turbidity (r2 = 0.85). Secchi disc depth (SDD) found the best fit for a power relation with NIR band reflectance (r2 = 0.74). The MODIS-Terra reflectance in red was found to be poorly related to in situ measurements. The relation in NIR reflectance was validated using the LOOCV (leave-one-out-cross-validation) technique and the fourth sampled data set collected on August 12–14, 2018. Developed models are validated with RMSE of 42.96 mg/l, 14.6 NTU, and 0.17 m, ARE of 23.3%, 27.6%, and 12.4%, and RRMSE of 25.1%, 44.5%, and 29.6% for SSC, turbidity, and SDD, respectively, using LOOCV. The equation was also validated using August 2018 collected data sets with RMSE of 87.6 mg/l, 11.7 NTU, 0.08 m, ARE of 20.8%, 25.9%, and 28.8%, and RRMSE of 17.8%, 20.5%, and 27.9% for SSC, turbidity, and SDD, respectively. Applying the developed regression model, a 10-year time series of SSC from 2008–2017 for May-August was estimated and the trend was tested using the Mann–Kendall trend test. It was found that an increasing trend was observed from the period 2008 to 2017. The result shows that satellite data like the MODIS-Terra imagery could be used to monitor and obtain past records of SSC with the developed equation. The increasing SSC can be reduced by implementing selected management practices in the surrounding watersheds of the lake to reduce nutrient and sediment inflow.

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