Investigation Of The Spatial And Temporal Variation Of Sediment Yield And Surface Runoff In Offa Watershed
(A Case Study Of Kwara State)
The exploration of the spatial and temporal dynamics of sediment yield and surface runoff in the Offa Watershed is a critical endeavor that delves into the intricate patterns of sediment transport and water flow over time. This study engages in a meticulous examination of the geographical and temporal shifts in sediment yield, unraveling the complex interplay between land use, precipitation, and hydrological processes within the Offa Watershed. By scrutinizing the spatial distribution of sediment yield and surface runoff, this investigation seeks to discern the influencing factors and patterns that govern sediment transport and runoff dynamics. Furthermore, it aims to elucidate how various land use practices and climatic conditions contribute to the observed variations in sediment yield and surface runoff over distinct time periods. This comprehensive analysis not only enhances our understanding of the environmental dynamics within the Offa Watershed but also provides valuable insights for sustainable watershed management practices, emphasizing the intricate connections between land use, precipitation, and hydrological processes.
In this research, an hydrological modelling tool, soil and water assessment tool (SWAT) used to investigate the spatial and temporal variation of sediment yield in a watershed. The model was run for 31years using spatial data such as Digital Elevation Model, soil map, land use and precipitation, wind and solar radiation. The results showed that the maximum value ofsurface Runoff was estimated as 19100.034mm in the year 2005 while the minimum surface Runoff was 1000.671mm in the year 20017. The maximum value of sediment yield was estimated as 2340.532mm in the 2005 and the minimum value was estimated as 34.769mm in the year 2003
Title page
Certification
Dedication
Acknowledgement
Abstract
Table of content
List of Figures
CHAPTER ONE:
INTRODUCTION
1.1 Introduction 1
1.2 Problem Statement 2
1.3 Aims & Objectives 2
1.4 Justification 3
1.5 Scope of Study 3
1.6 Description of Study Area 3
CHAPTER TWO:
LITERATURE REVIEW
2.0 Literature Review 5
2.1 Sediment Source Analytical Techniques 5
2.2 Sediment Yield Measurements 6
2.3 Field Measurements of Sediment Yield 7
2.4 Sediment Yield Modeling 7
2.5 Brief Description of Selected Hydrology Models 8
2.5.1 RIBASIM 8
2.5.2 WEAP 9
2.5.3 Realm Resource Allocation Model 9
2.5.4 HSPF Model 10
2.5.5 AGNPS Model 10
2.5.6 SWAT Models 11
2.6 SWAT Model Description 11
2.7 Water Shed Hydrological Modeling. 11
CHAPTER THREE:
METHODOLOGY
3.0 Methodology 13
3.1 Model Selection and Description 13
3.2 Model Input Data 14
3.3 Digital Elevation Model (DEM) 14
3.4 Soil Map 15
3.5 Weather Data 16
3.6 SWAT Model Set-up and Run 16
3.7 Water Shed Delineation 16
3.8 Land use map of the watershed 17
CHAPTER FOUR:
RESULTS AND DISCUSSION
4.0 RESULTS 19
4.1 Temporal Variation of total means for surface runoff 19
4.2 Temporal variation of total means for sediment yield 20
4.3 Temporal variation of annual means for sediment yield 21
4.4 Temporal variation of annual means for surface runoff 21
CHAPTER FIVE:
CONCLUSION AND RECOMMENDATION
5.0 Conclusion 23
5.1 Recommendation 23
References
1.1 INTRODUCTION
Water is an integral part of life, as human beings derived from the environment several services that are necessary for the survival, Water is one of the basic needs that human beings cannot live without; indeed water is life! Therefore, water-related (hydrological) ecosystem services provided by the environment (e.g provision, regulation and purification of freshwater) are quite valuable and important for human well-being. This underscores the importance of sound watershed management for continued provision of hydrological ecosystem services. From a hydrological point of view, a watershed includes all land contributing water (surface and ground water) to a reference point.
It is therefore obvious that land comprising of any watershed would generally be under other uses such as forests, agriculture and urban centers, which might commonly be considered ‘primary’ land uses. This means that watersheds provide other important ecosystem services, beside provision of hydrological ecosystem services. In some cases, enhanced provision of some ecosystem services may also lead to reduced capacity of watersheds to provide other services e.g. intensive cultivation to maximize food production may also lead to increase in soil erosion and consequently degradation of water quality.
Sediment yield is the amount at a point of interest in a particular period of time which occur due to heavy rainfall, are normally as tones per year or kilogram per year.
A large part of failure to achieve reasonable estimates of average annual sediment lies in particles of extrapolating relationship derived from field data with no consideration of appropriateness for future conditions.
Sediment yield is affected by many factors such as climate, soil, relief, vegetation and human influence. Runoff refers to as the part of water cycle that flow over land as surface water.
Runoff has been used as a variable representing climatic conditions and includes not only the water that travel over the land surface and through channels to reach a stream but also interflow, the water that infiltrates the soil surface and travels by means of gravity toward a stream channel.
In this study offa water shed is simulated to predict the surface runoff and sediment yield. The spatial and temporal variation obtained can be used as a decision support tool in the management of the water shed.
1.2 PROBLEM STATEMENT
Recent flooding issues in Nigeria as a result of excessive rainfall has resulted into runoff and sediment yield in the area. Therefore in order to manage the water shed sustainability, it is necessary to predict the variation of sediment yield and runoff in the area which can serve as a data base in managing the watershed.
1.3 AIM AND OBJECTIVES
The aim of the research was to investigate the spatial and temporal variation of sediment yield and runoff in Offa watershed.Specific objectives achieved are:
i. Predict the surface runoff and sediment into watershed
ii. Develop temporal variation map of sediment yield and runoff
iii. Develop spatial variation map of sediment yield and runoff
1.4 JUSTIFICATION
The Spatial and temporal variation of sediment yield and runoff in the catchment area can serve as a decision support tools to water managers in the area to plan a sustainable management of the water shed.
1.5 SCOPE OF STUDY
The scope of the work was limited to the study of temporal variation of sediment using temporal data of 31years from 1986 to 2016. the analysis was based on preliminary modeling results obtained from digital elevation model (DEM) land use and soil map to predict the optimum variation of sediment yield and runoff generation in Offa water shed.
1.6 DESCRIPTION OF STUDY AREA
Offa water shed is located in offa local government area of kwara state Nigeria. It is one of the main water supply in its locality, it is about 43km from Ilorin the capital of kwara state it fall within the latitude 8.1393o N and 4.71740 E. The map is shown in figure 1.1-1.3
SHARE PROJECT MATERIALS ON:
Investigating the spatial and temporal variation of sediment yield and surface runoff is a crucial aspect of understanding and managing water resources and erosion processes in a given area. Here is a general guide on how you can approach such an investigation:
1. Study Area Selection:
- Choose a study area that represents a range of land uses, soil types, and topography. Ensure it is large enough to capture meaningful variations in sediment yield and runoff.
2. Data Collection:
- Meteorological Data:
- Collect rainfall data, including intensity, duration, and frequency. Use rain gauges and meteorological stations.
- Gather temperature and humidity data to understand the climatic conditions.
- Hydrological Data:
- Measure streamflow and discharge at key points using flow gauges.
- Install sediment samplers to collect sediment samples over time.
- Geomorphological Data:
- Conduct a detailed survey of the topography and land use patterns.
- Identify and map soil types in the study area.
3. Remote Sensing and GIS:
- Use remote sensing data to analyze land cover changes and vegetation health.
- Utilize GIS to create spatial maps of the study area, integrating topography, land use, and soil data.
4. Field Surveys:
- Conduct field surveys to validate and supplement remote sensing and GIS data.
- Measure soil erosion rates and sediment transport in various locations.
5. Laboratory Analysis:
- Analyze sediment samples for particle size distribution, organic content, and mineral composition.
- Correlate laboratory results with field data to understand sediment characteristics.
6. Modeling:
- Utilize hydrological and sediment transport models (e.g., SWAT, HSPF) to simulate runoff and sediment yield.
- Validate the models using observed data and adjust parameters as needed.
7. Temporal Analysis:
- Analyze data over different time scales (daily, monthly, seasonal) to identify patterns and trends.
- Consider long-term trends in climate and land use changes.
8. Spatial Analysis:
- Examine spatial patterns of sediment yield and runoff across the study area.
- Identify hotspots and areas prone to erosion.
9. Data Integration:
- Integrate all collected data into a comprehensive database for analysis and interpretation.
- Use statistical methods to identify significant relationships between variables.
10. Report and Recommendations:
- Prepare a comprehensive report detailing findings, methodologies, and recommendations.
- Propose strategies for erosion control and sustainable land management based on the study results.
11. Monitoring and Adaptive Management:
- Implement a monitoring program to assess the effectiveness of recommended measures.
- Adjust strategies based on ongoing observations and new data.
12. Communication:
- Communicate findings to relevant stakeholders, such as local authorities, environmental agencies, and communities.
Conclusion:
Understanding the spatial and temporal variation of sediment yield and surface runoff requires a multidisciplinary approach, combining field measurements, remote sensing, GIS, laboratory analysis, and modeling. This comprehensive investigation can provide valuable insights for sustainable water resource management and erosion control