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| dc.contributor.author | Regasa, Zelalem | |
| dc.date.accessioned | 2020-06-12T07:11:52Z | |
| dc.date.available | 2020-06-12T07:11:52Z | |
| dc.date.issued | 2019-10 | |
| dc.identifier.uri | http://hdl.handle.net/123456789/11044 | |
| dc.description.abstract | Discharge from basins joining a lake is the main factor determining the lake volume, sedimentinflow,andturbidityofthelake. Suspendedsediment/orsolidsisanimportant parameter for describing the water quality of aquatic ecosystems. Lake Tana is an important and largest lake in Ethiopia for the local ecological system. However, environmentalchangeandanthropogenicactivitiesintheareathreatenitswaterquality. Suspended sediment measurements in the lake waters have been obtained from cruise samples. It is thus difficult to achieve and compare spatial and temporal SSC patterns forthelakeoveraperiodofyearsusingconventionalmethods. Thisstudyusedremotely sensed and in-situ data to characterize the spatial and temporal distribution of SSC in the wet/or rainy season. Moderate Resolution Imaging Spectroradiometer (MODIS) 250-m images are used as they are potential resources capable of monitoring sediment concentration records. Four sampling campaigns 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 was used for calibration of regression models. MODIS-Terra reflectance of remote sensing image data 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) was found best fit to a power relation with (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 LOOCV technique and the fourth sampled data set collectedonAugust12-14, 2018. TherelationsarevalidatedwithRMSEof42.9.6mgl−1, 14.6NTU,0.17m,AREof23.3%,27.6%,12.4%andRRMSEof25.1%,44.5%,and29.6% for SSC, turbidity, and SDD respectively, using LOOCV. The relation also validated for August 2018 collected data sets with RMSE of 87.6mgl−1, 11.7NTU, 0.08m, ARE of 20.8%, 25.9%, 28.8% and RRMSE of 17.8%, 20.5% and 27.9% for SSC, turbidity, and SDD respectively. Applying the developed regression model for suspended sediment, a 10-year time series of SSC from 2008-2017 for May-August was retrieved for Lake Tana and trend test for upward or downward trend was tested using the Mann-Kendall trend test. It was found that an upward trend from the period 2008 to 2017, indicating that the water quality of Lake Tana is deteriorating in space and time. Satellite data like MODIS-Terra image could be used to monitor and obtain past records of SSC. Management measures need to be implemented in the surrounding watersheds of the lake to reduce nutrient and sediment inflow. | en_US |
| dc.language.iso | en | en_US |
| dc.subject | Engineering Hydrology | en_US |
| dc.title | Estimation Of Suspended Sediment Concentration From Remote Sensing And In-Situ Measurements Over Lake Tana, Ethiopia | en_US |
| dc.type | Thesis | en_US |
