Prediction of Sediment Yeild to Lake Ziway Reservior and Assessing Reduction Methods (Using ARC-SWAT)
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Date
2021-04
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Addis Ababa University
Abstract
High sediment accumulation from watershed is the result of poor land use practices ,in appropriate management system and lack of suitable soil and water conservation measures .The main objective of this study is to estimate sediment yield from Lake-ziway watershed using soil and water assessment tool(SWAWT ) model.
Simulation was carried out using metrological and spatial data by dividing into 11 sub basin with 116 hydrologic response units (HRUs) with calibration period (2001-2009) and validation period (2010-2012). The simulation were performed using monthly time step both for Flow and sediment data using Sequential Uncertainty Fitting(SUFI-2).With in Calibration of uncertainty program (SWAT-CUP),the model performance indicators Coefficient of Determination (R2),Nash-Sutcliffe model efficiency(NSE) varying between 0.72-0.76,0.72-0.84 for both discharge and sediment respectively.
The simulated average annual sediment yield to Lake Ziway watershed was 2.69ton/ha/yr and the gross sediment entering to the lake was estimated to be 1.04 million ton/yr with 38.5% of deposition rate. The Spatial Variability of annual sediment yield rate is between 0.19ton/ha/yr to 6.74ton/ha/yr throughout the basin and Sub-Basin 4 and 5 were detected to be the hot spot Catchments with sediment yield value greater than 6 ton/ha/yr.
For management Scenario, Taking the existing condition of the watershed as a baseline scenario for reference purpose, three scenarios were built. The first scenario, terracing reduces Average sediment yield by 72% from 2.69 Mton/ha to 0.76Mton/ha. While filter strips reduces Average sediment yield by 42% from 2.69 Mton/ha to 1.56Mton/ha and grassed water ways by 58% from 2.69 to 1.12 Mton/ha.
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SWAT model, SUFI-2, SWAT-CUP, Sediment yield, Lake Ziway watershed