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Future Climate Impact Under CMIP5 RCP Scenarios on Maize Water Requirement and Growth Period, Land Suitability Evaluation and Sediment Yield Modeling for Sustainable Land Use Planning and Management: A Case of Lake Hawassa Watershed

PIs:  Rediet Girma and et al., 2021

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Executive summary

The meteorological data were interpolated using high-intensity stations distributed over the Lake Hawassa watershed. Two GCMs (CNRM5 and CSIRO-MK-3-6-0) were used for future climate change projections over the Lake Hawassa watershed under the RCP4.5 and RCP8.5 scenarios. Therefore, RCP4.5 and RCP8.5 were taken to be suitable for studying the impact of climate change over the Lake Hawassa watershed for crop growth period and crop water requirement because they have the ability to consider the moderate and extreme scenarios required for planning a better management strategy. The period from 1980 to 2010 is defined as the baseline period in this study, where the future impact of climate change on the length of growth periods (LGP) and crop water requirement (CWR) are analyzed. Soil physical property analysis was demonstrated to assess the suitability of soil properties for Maize production.

The crop water requirement of Maize, under RCP4.5, is 518.1mm by 2020s, and 528.4mm by 2080s, respectively for the initial growth period. For the same scenario (RCP4.5) Maize shows an increment in the CWR from 2072.4mm to 2213.25mm from the 2020s to the 2080s, respectively. During the late season, there was also a remarkable increment in the CWR of Maize up to the end of the 21st century. The future growing season of the area is projected between April 15 to May 1 onset time and the end of September is the cessation time with LGP ranging between 150-160 days. Even though the future is estimated to be suitable for rain-fed agriculture. In general, comparing the past and the future growing season of the area, there was a time when both Bega (between October and February) and Belg (stays from March to May) remained mostly not operational for the rain-fed agriculture, but the future is anticipated to be suitable for rain-fed agriculture during Kiremt (stays from June to September). There is also a considerable change in the onset time from April to May and offset time from September to October and a decrease in the length of the growing season is an early warning that requires redesigning the traditional agricultural practice and utilizing the anticipated rainfall optimally for the future periods.

Land is one of the most important natural resources, and maintaining it in good health, is very much needed for meeting out the increasing demands. Land degradation is severe in the Lake Hawassa catchment so a high sediment inflow rate and the increasing trend of runoff from the watershed are delivered to the Lake manifested by land-use changes, deforestation, misuse of land resources and/or unsustainable use of land. Thereby, biophysical and socio-economic land suitability analysis is a prerequisite for sustainable agricultural practices. It is of dominant importance to identify and assess suitable land for various uses in a sustainable manner by optimizing land resource utilization while causing minimum impact on the environment. It is, therefore, vital to identify, analyze, describe and prioritize problems linked with land-use practices to set development objectives and key interventions/actions based on the findings of this project in order to address all components and factors affecting the characteristics and functioning of the watershed.

The study was generally comprised of the following major objectives/sub-components: Impacts of climate change under CMIP5 RCP scenarios on maize water requirement and growth period, a case of Lake Hawassa watershed; Evaluating biophysical parameters for land suitability study in Lake Hawassa watershed, Ethiopia: a methodological study for agricultural land use planning and management; Comprehensive socio-economic land evaluation for land use planning and sustainable land management: the case study of Lake Hawassa Watershed, Ethiopia; Mapping runoff and sediment yield susceptibility of the Lake Hawassa Watershed, Ethiopia.

The methodology followed for the respective component is summarized as follows: Impacts of climate change under CMIP5 RCP scenarios on maize water requirement and growth period (component 1) was conducted by using CMIP5 model outputs of CNRM and SCIRO under RCP 4.5 and RCP 8.5 scenarios. Biophysical land suitability analysis (i.e., resource surveys and interpretation) was attained using ArcGIS version 10.7.1. The socio-economic analysis was carried out using VIKOR-AHP method developed as a Multi-Criteria Decision Making (MCDM) to solve problems with conflicting or non-commensurable criteria. Hence, socio-economic criteria will be weighted, and alternatives are ranked using the integrated VIKOR-AHP method. The fourth component focuses on the amount of the runoff and sediment yield from the Hawassa lakes watershed using SWAT model, and asses/evaluates the relationship between the runoff and sediment yields. Finally, outputs from each component were documented and monitored for future decision-making processes and possible interventions.


Assessing the carbon stock potentials, land degradation processes, and Impact of climate change on Hydrology and Watershed Prioritization in Lake Hawassa Watershed, Ethiopia

Zemede Mulushewa et al., 2020

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Ethiopia is one of the countries most affected by severe degradation of natural resources, including deforestation, soil erosion, and climate change, and shrinking and disappearing of water bodies. The rates of soil erosion and land degradation are frighteningly high. Crop and livestock production and energy supply situations are at risk. The human health situation is dreadful. As a consequence, drought, low agricultural productivity, and food insecurity are common features of the country.

Lake Hawassa watershed is located within the Central Main Ethiopian Rift Valle. Geographically the watershed lies between 6o49’N to 7o15’N latitude and 38 o17’E to 38o 44’E longitude.  Lake Hawassa is a fresh closed lake playing an important role in the lives of many people in the SNNPR. Despite its importance in a wide spectrum of purposes, the Lake Hawassa Watershed is under serious threat due to anthropogenic factors. It has bitterly experienced the consequences of severe loss of forest cover while recurrent drought and crop failure, loss of topsoil, and land degradation are common in the watershed. This all has resulted in severe land degradation, reduction in agricultural productivity, and siltation of Lake Hawassa. This will have a profound impact not only on the natural resource base but also on the livelihoods of the farmers confined within the wide plains and mountainous landscapes surrounding the lake.

It is, therefore, vital to identify, analyze, describe and prioritize problems of the watershed to set development objectives and key interventions/actions in order to address all components and factors affecting the characteristics and functioning of the watershed.

 The proposed study will comprise four components:

  • Estimating and mapping carbon Stock to mitigate climate change across different LULC by using remote sensing and ground truth in Lake Hawassa watershed, Ethiopia
  • Evaluating the Impact of Land use/cover conversion on Run-off, Soil Loss, and Sediment Yield Response Using Geospatial Technology in Lake Hawassa watershed;
  • Evaluation of climate change impact on the hydrology of Lake Hawassa watershed, Ethiopia.
  • Watershed Prioritization based on Morphometric Parameters and Land Use/Land Cover Analysis: The Case Study of Lake Hawassa Watershed, Ethiopia

Finally, all outputs (i.e., LULC, soil erosion, carbon stock, sub-watershed prioritization and climate change impact on the hydrology interpolation) of each component will be mapped and monitored by using a web GIS-based integrated approach to make Lake Hawassa watershed for better management of watershed.  

The methodology to be followed for the respective component is presented in the following sections in detail.  Estimating and mapping carbon stock potential to mitigate climate change by using remote sensing and ground truth (component 1) will be conducted by using high-resolution satellite images (i.e. object-based image analysis) and the ground survey method.  Estimating soil erosion and runoff modeling via using Geospatial Technology will be performed by using Landsat TM imagery, AVSWAT model integrated with remote sensing, soil map, runoff data, and related materials/methods as presented in (component 2). Watershed Prioritization based on Morphometric Parameters and LULC (sub-project 3) will be done by using geospatial technology and ground truth data as presented in respective sub-project methodology sections. Evaluating climate change's impact on the hydrology of the Lake Hawassa watershed will be done by evaluating all water balance components in detail and the CC impact will be projected until the end of the 21st century (see more details in Sub-project 4). Finally, the output of components 1-4 will be mapped and monitored for future and updated technology use in a web-GIS-based integrated mapping and monitoring of LULC, soil erosion and carbon stock of Lake Hawassa Watershed. 

The overall objective of this study is to estimate/ map carbon stock, soil erosion and runoff modeling, prioritize watershed and evaluate climate change's impact on hydrology; furthermore, to identify suitable interventions in Lake Hawassa watershed.  

Therefore, for successful and sustainable watershed management, an integrated and participatory approach is necessary to accomplish essentially different objectives and address the agendas of different stakeholders with a collaborative watershed vision and holistic focus on challenges and opportunities prevailing in the Lake Hawassa watershed.

As a consequence, the watershed development plan has become mandatory, and integrated watershed management based on morphometric and LULC parameter analysis to recognize the overall status of the watershed will be required.

Internet GIS combines the advantages of both GIS and the Internet. Geographic information can be distributed in a variety of forms on the Internet. Moreover, as Internet technology takes to progress, web-based GIS applications also change. The terms web GIS and web mapping remain somewhat synonymous. Web GIS uses web maps, and end-users who are web mapping are gaining analytical capabilities. Web mapping is the process of using maps delivered by geographical information systems (GIS). Most of the maps display information about the natural resources available around. A web map on the World Wide Web is both served and consumed, thus, web mapping is more than just web cartography, it is a service by which consumers may choose what the map will show. 

The exponential Internet growth and the global connectivity reached in the last few years have had a great impact on the requirements of contemporary and next-generation information systems. Fundamental characteristics include efficient data access, delivery over the Web, heterogeneity, and interoperability.  The primary focus of Internet/Web use for mass distribution and presentation of public information has moved to the distribution of software services over intranet, extranet and Internet. Next-generation information systems are going to be assembled of specialized Web services (components) that are self-contained, self-describing, modular applications that can be published, located, and invoked across the Web using a wide spectrum of Web-enabled stationery (desktops, workstations, Web TV) and mobile devices (PDAs, mobile phones, laptops, handheld computers.  

Thus, Integrated and participatory watershed development is managed and developed eco-friendly to other natural resources, which are capable of addressing many natural, social and environmental intricacies.  However, in the Lake Hawassa watershed the farmers and most of the stakeholders were not aware of the major constraints for the increasing potential of the watershed specifically in terms of carbon trading, natural and environmental aspects. Therefore, in order to break these intertwined problems, integrated and participatory watershed management and development-oriented research is required.

The general objective of this study is estimating and mapping Carbon stock to Mitigate Climate Change by using remote sensing and ground truth; estimating Soil Erosion and Runoff Modeling via using Geospatial Technology and mapping/ monitoring lake watershed for a better future via a web-GIS based integrated of LULC, soil erosion and carbon stock.

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