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International Riversymposium


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28 September 2021
9:00 am - 10:30 am - 28 September 2021

Opening Ceremony

Riversymposium - Room 1 - In-Person
Chair: Prof Paul Greenfield, Chair IRF

9:10 am

2. Michael Wilson, Chief Executive, Australian Water Partnership, Australian Government
3. Hon Glenn Butcher MP, Minister for Regional Development and Manufacturing and Minister for Water, Queensland Government
4. Lord Mayor Adrian Schrinner, Brisbane City Council
5. Peter Varghese, Chancellor, University of Queensland - In person

10:00 am

Speaker: Hugh Possingham, Queensland Chief Scientist
28 September 2021
10:30 am - 11:00 am - 28 September 2021

Morning Tea Break

28 September 2021
11:00 am - 12:30 pm - 28 September 2021

LIT: Report Cards

Riversymposium - Room 3 - Online
Chair: TBA

11:00 am

Presented by: James River
11:00 am - 12:30 pm - 28 September 2021

Understanding River Systems 1

Facilitator: TBA

11:00 am

Decision Support Systems like GIS (Geographical Information System) can be powerful tools in helping communicate the condition of our waterways and identifying pressures affecting them. Healthy Land and Water, with the help of its partners has collected a wealth of data on the condition of South East Queensland’s (SEQ) waterways (freshwater, estuarine and marine). 

With over 20 years of data, displaying information that is simple and easy to interpret can be challenging. GIS software is effective in presenting the condition of the rivers, and their change over time. Healthy Land and Water has created online data dashboards using desktop and online GIS and data display tools like ESRI ArcGIS and Microsoft PowerBI. The data dashboards display the condition of waterways of SEQ based on a suite of routinely measured water quality, habitat, and ecological indicators. Additionally, since 2015, HLW surveys the local community’s perception of waterways which in turn are available in online data dashboards. 

The dashboards are interactive, and users can customize what information is displayed, ranging from high level summaries (waterway grades) to trends and correlations between individual indicators.  These display tools facilitate the engagement of local communities in understanding the health of our local waterways, inspiring the public and stakeholders to take action to improve their health. 

These tools represent a substantial step towards a near-real time understanding of the health of our waterways. This wealth of data is also allowing predictions of the future conditions of waterways to be made under a range of future scenarios. Both near-real-time monitoring, and predictive capability is allowing for improved natural resource management decision making.

11:15 am

All along the Queensland coastline vast amounts of sediment are travelling through waterways and into coastal environments during large rainfall events. Brisbane River is no different. The Brisbane River floods in 2011 and 2013, as well as more recent minor events, have generated massive amounts of sediment that flow from the catchment, through Brisbane River and into Moreton Bay causing numerous environmental and economic consequences. 

The large amounts of sediment entering Brisbane River are not natural. We are only a couple of days of very heavy rainfall away from another environmental disaster. However significant progress has been made in understanding this important problem. In this presentation, learn about what the Port of Brisbane, based at the mouth of the Brisbane River, is doing to manage this challenge. 

11:30 am

There is a growing movement towards citizen science – public participation in scientific research to increase knowledge of the environment. Fitzroy Partnership for River Health operates a unique citizen science program with a dedicated Science Officer supporting schools, groups and individuals to sample and test their local waterways and upload their results to their website portal, MyWater. As well as increasing understanding and awareness about
the contributors to waterway health, Fitzroy Partnership aims to build one of the largest citizen science water data samples in Australia!

11:45 am

The Reef Trust Partnership, a landmark agreement between the Australian Government and the Great Barrier Reef Foundation, commits $201m to improve water quality flowing to the Great Barrier Reef. As the partnership approaches its halfway mark, this presentation will discuss the approach, outcomes, lessons, and challenges associated with this six-year investment. 
The partnership has been guided by a strategic approach to implementation, that has been underpinned by governance arrangements and decision-frameworks to maximise the water quality benefit that can be delivered from the available funding.  Significant lessons have also been learned regarding the promotion of innovation in water quality improvement, both via a dedicated $10 million innovation program, as well as through embedding innovation across the portfolio of projects. 

12:00 pm

The Dja Dja Wurrung is an Aboriginal Australian people whose traditional lands include the Bendigo region of central Victoria, Australia. They have developed a Healthy Country Plan to guide their re-connection to Country and rights as Traditional Owners. The Plan outlines many goals, including the desire to have healthy waterways to meet the needs of their people and land. 
One such goal is to self-manage the water of the Lake Boort, Lake Lyndger and Kinypanial Creek system with appropriate planning and governance arrangements. There are many threats to this system including recreational uses, grazing, pest plants and artificial flooding. The protection and restoration of this system is critical to preserve cultural and natural values of this important area.
To better understand the system, an ecological and hydrological study was completed to review the watering required to support the known ecological values in Lake Boort, Lake Lyndger and Kinypanial Creek. The system receives water from a variety of sources and the ecological and cultural values supported by delivery of a given volume of water are highly dependent on the source and pathway of water. 
The volumes of water required are dependent on the pathway and what ecological values are being targeted. The estimated volumes of water to provide a single watering event that supports all ecological values in this system are very considerable and come at significant financial cost.
In this presentation four hypothetical water delivery scenarios will be discussed, representing a suite of possible pathways in which water could be provided to support the water requirements. The presentation will also discuss how other sources of water (e.g. natural catchment inflows or water provided for aesthetics/recreation) could potentially be leveraged to optimise the efficiency of future managed water deliveries to the study area.

12:15 pm

The Port of Brisbane is located at the mouth of the Brisbane River adjacent to Moreton Bay. The Port of Brisbane is a cornerstone of the Queensland economy being one of Australia’s fastest growing container ports and the state’s largest multi-cargo port. The goal of the Port is to grow trade through the port in a sustainable manner. 

The port takes its environmental management responsibility seriously. The port operates both within and adjacent to sensitive and important ecological receptors including international protected wetlands, seagrass, mangroves, corals and a variety of terrestrial and marine fauna including migratory shorebirds. Environmental management at the Port of Brisbane is underpinned by an ISO14001 Environmental Management System and an innovative environmental monitoring and research program that has generated many interesting findings. 

Being at the mouth of a major river system, the Port of Brisbane is subject to impacts outside its sphere of control. Despite the inability to directly control these aspects, the Port continues to invest heavily in environmental management and monitoring to improve understanding of the environment at the mouth of the Brisbane River and inform ongoing management decisions both internally and externally.  
11:00 am - 12:30 pm - 28 September 2021

Understanding River Systems 2

Facilitator: TBA 

11:00 am

The coastal ocean assessment for sustainability and transformation (COAST card) project has taken the establishment of stakeholder engagement as an important issue and has begun collecting basic information for conducting Social Network Analysis. The targets are the Chesapeake Bay in the United States, Tokyo Bay in Japan, Ishigaki Island-Sekisei Lagoon, Manila Bay in the Philippines, and the Goa coast in India.
As a preliminary study, we created an organization Influence grid for each target area using the interest and influence of the bay / sea area as an index. When the attributes of the parties involved were classified into Academia, NOGs, Governments, Industries or Companies, and Public, common characteristics emerged in each bay and sea area.
For example, Industries or Companies have a strong influence, whether they are interested or not. Although Academia has a strong interest, its influence is relatively small and varied. NGOs and Public are distributed so as to be inscribed in Academia. For Governments, there are ministries with high interest and influence and ministries with low interest and influence, reflecting their multipolar organizational structure.
We would like to discuss how we can approach these stakeholders and change their consciousness for sustainable bay / sea and watershed management.

During the colonization period over the past several hundred years, many streams in the arid regions of Australia, Mexico, and western United States have been tapped to feed agricultural operations, quench the thirst of rapidly growing cities, generate electricity, and sustain recreational enterprises, while simultaneously neglecting the rights of indigenous communities and the rivers themselves. Rivers of all sizes have been tamed, confined, drained, and re-routed to the point where they are a mere whisper of their former free-flowing expression. And yet, the historic and current stream flow regime remains the guiding star for the objectives, strategy, and adaptive management actions that define a restoration plan. At the 2007 International River Symposium in Brisbane, Australia, environmental flow was defined as “the quantity, timing, and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and well-being that depend upon these ecosystems” (Brisbane Declaration 2007). In the recently published guidebook on river restoration: Renewing Our Rivers (2020), nine environmental flow practitioners that were inspired by the 2007 River Symposium on flows crafted a collective story of their geographically diverse efforts to protect local streams from further human interferences by securing and managing flows to support restored habitat, ecohydrological, and cultural values. This presentation will highlight experiential insights and strategies presented in the guidebook to protect or enhance streamflow, including: 
·      Assessing the need for an environmental flow program,
·      Inventorying water supplies, demands, and opportunities,
·      Sharing environmental flow strategies and lessons learned from the field.
Key case studies will be highlighted to summarize the combined wisdom from on-the-ground restoration experiments and successes in North America and Australia and will present insights about future river restoration efforts that will be defined by climate change, increasing water scarcity, and emerging innovation. 

11:30 am

Among threats to farming communities in the southern region of Punjab, Pakistan; are increasing groundwater depletion and monsoon floods. Our research addresses increased community resilience by considering these two phenomena together. Although the Punjab province is situated in the Indus River Basin, with mighty rivers sourced by snow and glacial melt, about half of agricultural water and over 90% of drinking water demands are currently met from groundwater. Unregulated pumping through approximately 1.2 million private tubewells is adversely impacting the quantity and quality of groundwater and adding extra financial burden to irrigators. Most mitigation approaches focus on demand management, but in Southern Punjab the Provincial government is also experimenting with increasing the supply of groundwater via Managed Aquifer Recharge (MAR), using floodwater. While floods can cause extensive damage to humans and their properties, they can have numerous ecosystem benefits. In this trial floodwater from the Sutlej river is to be diverted into the bed of the (abandoned) old Mailsi canal, in which 144 recharge wells have been constructed. This associated Ph.D. study is considering both biophysical and institutional aspects of the MAR trial, with some of the biophysical findings presented here. Groundwater level data from 2010 to 2020 from 25 piezometers in the study area have been analyzed. The area has been divided into 25 polygons; each polygon attributed to a piezometer. The volume of water which can be stored underground has been estimated using specific yield method.  Based on preliminary studies potential of storage of floodwater in the aquifer has been found 4.78 km3 during the year 2019. As the water levels are falling in the area this storage potential will increase over time. This work suggests that there is value in further pursuing research regarding MAR for increasing resilience for communities in this agricultural area. 
Key Words: Groundwater, aquifer, managed aquifer recharge, Punjab, Pakistan

11:45 am

 Being aware of a river’s personality and position in the resilient spectrum is of utmost importance in the journey towards river resilience. The river personality is characterized based on geology, geography, landscape topography, political governance structures, culture, and economics. The journey of a river is characterized based on certain actions and drivers of the community. In terms of discharge and drainage area, Mahaweli is a highly significant river and it holds one-seventh of overall runoff in Sri Lanka which occupies 15% of the country. Kelani River is home to more than a quarter of the country’s population and over 10,000 industries rely on the basin's natural resources and services. According to real information, the Mahaweli and Kelani rivers have seminal and supplier river personalities, respectively. Both rivers are in the reconciliation phase of the journey towards resilience. However, according to a survey depicting public awareness, most of the respondents (22.5%) labelled river Mahaweli to have an iconic personality while only 10% of responses reflected  a seminal personality. The highest (30%) number of respondents had placed Kelani river as a recurrent river while only 4.3% had considered the river to have a supplier personality.  Considering the position on the spectrum, Mahaweli river was categorized under exploitation phase (2%), mitigation phase (21%) and reconciliation phase (17%). Kelani river was categorized under mitigation phase (50%) and reconciliation phase (50%). This depicted that the community is unaware about crucial information such as the condition of water discharged into rivers, the economic and recreational uses of the river, cultural significance and current management strategies. Therefore, it is important to raise  awareness on these specific areas among the public as it is important to highlight the current status and importance of conserving rivers rather than conducting superficial conservation programs in Sri Lanka. 

Keywords: Journey , Kelani, Mahaweli, Personality, Resilience 

12:00 pm

Ensuring rights and perspectives of local communities in water decision making process is essential for long term strong water governance arrangements. One way to ensure human rights are embedded in water governance is through its explicit and direct inclusion in research programs that support localized water decision-making. The Sustainable Mekong Research Network (SUMERNET) is one such research program that through partnerships delivers ground knowledge and action on water insecurity across six Mekong countries. This paper will develop a framework for human rights-based approach (HRBA) in water research which is then tested in a 5-year SUMERNET program. There were several positive results found. By framing water research program from HRBA, it creates the opportunities to strengthen and empower people and communities affected by water insecurity. It also ensures that decision-making process in water governance is a result of participatory approach that involve all stakeholders at different levels. At the same time, there are also challenges in applying the framework. The research found that some local elements need to be included into the framework to make it more applicable. Moreover, there are huge complexities of applying a HRBA as a framework in water research programs across Mekong countries as it is diverse and expansive.

The paper is based on review of literature, analysis of secondary data such as program documents and project proposals as well as primary data collection through interviews and workshops with project leaders of water research projects and program staff in Mekong countries.


Key words: human rights-based approach, research program, water research, lower Mekong countries, local context.

12:15 pm

 The Gin River is a crucial source of drinking water in the Galle district. However, its lower catchment is highly prone to floods. Therefore, it is a timely need to forecast and manage the Gin river watershed efficiently to avoid any water deficits and natural disasters. The major objective of the study was to model water flow in the Gin river of Sri Lanka. Hydrological model: HEC-HMS (Hydrologic Engineering Center-Hydrologic Modeling System) 4.5 was used to simulate the water flow along with ArcGIS for preparation of maps. Necessary input data for the models were collected from the Department of Meteorology and Irrigation Department, Sri Lanka. Data maps required for preparation of digitized land use maps and digital contour maps were obtained from the Survey Department of Sri Lanka. Calibration and Validation of the HEC-HMS model was done using the model parameters; Initial Constant Loss method, Snyder Unit hydrograph transform method and Constant monthly base flow method. The model was calibrated using data from 2009-2014 and validated using data from 2015-2019. The model was evaluated using residual method by analyzing the model residuals. The R2 value of the best calibration and validation were 0.70 and 0.78, respectively. In the best calibration, 73.7% and 92.3% of residuals were within +1SD and +2SD, respectively. In the best validation, 74.3% and 93.6% of residuals were within +1SD and +2SD, respectively. The results indicated that HEC-HMS 4.5 computer model can be used to simulate Gin river flow reliably, especially during high rainfall and flow conditions which could be used in flood predictions. Understanding the Gin river system plays a critical role in its journey towards resilience, and forecasting models such as HEC-HMS can be used as a major tool in this regard. 

Keywords: Calibration, Flow, Gin_river, HEC-HMS, Validation 
28 September 2021
12:30 pm - 1:30 pm - 28 September 2021

Lunch Break

28 September 2021
1:30 pm - 2:30 pm - 28 September 2021

Effective River Governance

Effective River Governance - Room 3 - Online
Facilitator: TBA

1:30 pm

 River pollution is a global challenge with serious impacts on human and ecological health. Governance, or lack thereof, is critical for tackling or exacerbating this issue. Existing research has focused on examining river governance in terms of transboundary relationships between nation states. The assumption is that national or international processes may drive on-ground changes in a top-down manner. Tracking of sustainable development targets has typically considered integrated water resource management (IWRM) as a country-led effort—requiring it reflected in national policies. 
While multilevel coordination is central to IWRM, there are concerns raised about the under-appreciated local capacities, which contribute to policy implementation successes or failures. Our research aims to narrow the knowledge gap by drawing on key literature to develop a framework for identifying enablers and barriers for river governance at the municipal scale, which will be applied to study policy implementation across municipalities in the Citarum River, Indonesia. The river is one of the most polluted worldwide. While the governments have promoted an integrated revitalisation approach, implementation success at the municipal scale varies. 
There is a growing body of literature on the kinds of institutional arrangements, local capabilities and political processes that can drive transformative changes at city-scale. The urban water scholarships offer insights into the socio-technical dynamics for transitions in cities. Also critical is understanding co-productive arrangements between state and non-state actors to promote shifts in planning and infrastructure regimes. Politics, the capacity to mobilise resources to accomplish policy outcomes, is another important aspect of urban planning. Enriched by these insights, our framework provides nuance on what municipal actors may or may not do in shaping river governance outcomes. 

1:45 pm

Floodplain Harvesting is one of the most complex and contested areas of water law in New South Wales (NSW), Australia. Floodplain harvesting refers to the method of capturing and storing floodwaters as it moves across the floodplain. This is a long-standing historic practice for irrigation farmers, particularly in the northern valleys of Australia’s Murray-Darling Basin, which face infrequent episodic flood events as part of the climatic extremes. 

Following the National Water Initiative (blueprint to Australia’s water reform), and subsequently the NSW Water Management Act 2000, all forms of water take in NSW needed to undergo a transition pathway to meet the contemporary paradigms of water management. These contemporary paradigms include requirements to hold a water access licence, meter and measure water take, and comply with legal limits on the total volume of water take. Floodwater is the final water source to undergo this transition in NSW, with the state currently amidst a significant and historic reform to do so, through the Healthy Floodplains Project.  This Project seeks to modernise floodwater management, and ensure appropriate sharing of floodwater between farmers, the floodplain environment, cultural values and downstream communities. However, the implementation process has been inundated with challenges. 

This presentation seeks to provide an outline of this critical point in the ongoing development of floodplain harvesting water law in NSW. In particular, this presentation seeks to share the perspective of the impacted farming industry, whom have largely accepted the reform process despite significant social and economic impacts to rural communities, including a 30% reduction in historic floodwater access by farmers in one valley alone. 

2:00 pm

 The rain-fed groundwaters on Minjerribah Island are an existing source of water that is of excellent quality and an integral resource for island and off-island communities.  Continued access and use of water present a microcosm of considerations of the challenges for achieving trusted management of water that balances economic uses, social and cultural values of water systems and the health and maintenance of groundwater dependent ecosystems. Climate change, population growth and urbanisation all place pressure on sustaining these freshwater ecosystems. Seqwater, as the regional bulk water provider in South-East Queensland, has a central role to play in managing these challenges and securing water supply of adequate quality and quantity for the region. However, society holds a range of expectations from Seqwater, as water is a public and vital good and its supply incurs direct and indirect societal, environmental and intergenerational costs. Increasingly regulatory compliance is insufficient to address these expectations for the diverse interests of community, government and business stakeholders. The concept of social licence to operate (SLO) was identified as an approach that can guide Seqwater in its actions to enhance the social acceptability of its operations. One of these operations is the groundwater extraction from Minjerribah. As a benchmarking step, a review of internal capacity was completed to assess adaptiveness to changing societal expectations, while maintaining water supply certainty. In this paper we will present initial findings of how SLO has been adopted by Seqwater to inform internal procedures to better manage the social license associated with a targeted outcome, namely a sustainable abstraction on Minjerribah, that considers ecological, social and local cultural values. The findings will highlight lessons and insights for how water authorities can integrate a social license approach and embrace more holistic approaches to water management when planning for water security. 

2:15 pm

Advancing Indigenous rights in water governance is high on the global agenda in addressing planetary health. The Citarum River in Indonesia is home to local Indigenous communities, predominantly known as the Sundanese peoples. It is also one of the most polluted rivers on the planet. Our project aims to find legal pathways to assist those communities to protect river health and the wellbeing of those who depend on the river for their water and livelihoods. Although there is emerging interest in understanding the role of local Indigenous communities and their culture in supporting the Citarum recovery and revitalisation, little is known about the kinds of legal reforms needed to advance their role and rights. 

In that respect, there are potential lessons to be learned from the Australian experience. Australia’s Indigenous peoples have advocated for legal recognition of their cultural knowledge and rights in relation to water governance for many years. Although progress in Australia is encouraging, there is no systematic overview of current laws and policies across all jurisdictions and how they facilitate Indigenous water rights. Our first objective therefore is to promote learning across cultural contexts by undertaking an in-depth study of the Australian legal landscape and recent reforms. Underlying these reforms is a recognition of the cultural and spiritual connection of Indigenous people with their land and waters and the important role their knowledge plays in sustainable water governance. This baseline knowledge is important to understand whether any of the Australian approaches could be appropriately adapted to Indonesia. Our next objective is to formulate an international research agenda on legal innovations for advancing Indigenous rights and sustainable river governance by leveraging existing Australia-Indonesia knowledge networks.

The project is due for completion in late 2021 so this presentation will outline the results of the project to date.   

1:30 pm - 2:30 pm - 28 September 2021

LIT: Brisbane City Council1000+

Riversymposium - Room 1 - In-Person
Chair: Eva Abal
1:30 pm - 2:30 pm - 28 September 2021

Understanding River Systems 3

Facilitator: TBA

1:30 pm

Ecological flow objectives in environmental water planning documents throughout SE Australia are currently not ‘climate ready’. ‘Climate ready’ is defined here as an aspirational goal to establish restoration targets today that are considered feasible under the future climate regime. The research presented here examines why climate considerations are currently not incorporated in environmental water planning. This paper will discuss key findings from interviews with water managers and an Australia wide online survey, which have been conducted as part of an industry PhD. 
Throughout Australia, flow restoration targets and flow regimes are predominately set by following state government methods which lack consideration of future climate and ecological change. While a few regional authorities have started to diverge from following these recommended methods in an attempt to incorporate future climate and hydrology, there is presently no agreed method. The majority of organisations included in the research see the need to include future climate, hydrological and ecological change in flow assessment methods.  
Most common reasons for organisations not being able to include climate considerations and adaptation in environmental flow management are a combination of long term planning issues such as using historic flow regimes and ecological reference points and general barriers such as insufficient resources, lack of political leadership and lacking of regionally specific information. 
The paper will also explore demand for additional information to reveal the need for fit for purpose hydrological and ecological models, vulnerability assessments, decision making tools that incorporate climate, hydrological and ecological science with socio-economic considerations to provide a range of options for future planning, and improved knowledge exchange between academia and industry. 

1:45 pm

The proposal to raise the Warragamba Dam remains one of the most heatedly contested and complex water management issues in Greater Sydney. A myriad of contentious stakeholders are present in the picture. Every stakeholder perspective has a slightly different understanding, and ultimately a different option.  Different values and ambitions are held across the board from both sides of politics, private industry sectors, academic and industry groups, Aboriginal and environmental conservation groups, to communities living in the area, and developers with notional support of State government encouragement, looking to support, or capitalise, on the growth and development of the Western Parklands City, and build more property for people to make their home in the floodplain. It is no surprise that at many a round table or panel discussion, explicit comment and opinion on the matter is generally avoided. 

Following on from baseline data collected in 2019 from a contingent valuation survey study on the proposed raising of the Warragamba Dam which compared society’s preference and willingness to pay for environmental and indigenous heritage conservation versus flood mitigation, the recent extreme rainfall events in March 2021, which resulted in flooding across many parts of the Western Sydney flood plain, has presented an interesting opportunity to look at how the understanding and perception of key stakeholders and the community have developed over time. This investigation provides an update on the status of the controversial water management project and the outcome of consultation with a range of key stakeholders and the community. This work encapsulates the notion of "Recovery to Resilience", and what it may mean in this context of a conflicting water management issue and the shaping of a river solution.  It is important to have these discussions, ask the difficult questions, and seek to address the issues.

2:00 pm

National River Linking Project (NRLP) has a long history of 125 years in India, which was initially conceived by Britisher for trade supply. This project comprises of 30 links connecting 37 major rivers across the country, the network of 300 storage dams with proposed benefits of 35 million hectares of irrigation, 34000 megawatts of hydropower, and incidental benefits of flood control, water supply, fisheries, pollution control etc. at the cost of INR 560000 crores as on 2002. The Ken-Betwa Link Project (KBLP) is the first project under this grand plan which has received the approval in recent times.  Amid all the criticisms to this project, this study proposes the economically cheaper, socially acceptable, and environmentally viable alternatives based on action-research work in the same region.  
In 2014-18, the community driven water management was demonstrated in 20 tribal villages in the upper catchment of River Ken. 14 lakhs cum water was augmented benefiting 500 households for irrigation and drinking water at the cost of INR 8/cum and INR 40000/ha as against the cost of KBLP of INR 175/cum and INR300000/ha (cost as on 2016). The demand side management practices like System of Rice Intensification, organic farming, indigenous varieties, etc. could enhance the water productivity by 25%. The comprehensive livelihood promotion at the cost of  INR 3000/family/year for three years could increase the income by INR 20000/family/year at the end of fourth and fifth year. 
The above socio-technical model is based on - participatory approach, traditional knowledge, capacity building of the communities, and governance by the people. This model has set up an alternative to counterview the benefits those have been promised by the grand project in the same region and proposes the need to change the investment patterns under major schemes to accommodate the region-specific solutions based on social-environmental-economical rational. 

2:15 pm

 Soil erosion from land surface and sedimentation of surface water bodies are major problems worldwide including Sri Lanka, especially in the upper Mahaweli catchment. To address these issues, a proper understanding of sediment delivery ratios of sub-catchments of the area is necessary. Therefore, a study was conducted with the objectives to estimate soil erosion from the Nillambe Oya watershed using the Universal Soil Loss Equation (USLE), to estimate the total annual sediment load in the Nillambe Oya and to determine the sediment delivery ratio of the Nillambe Oya watershed. The combination of USLE and sediment loads carried by the stream were used to estimate the sediment delivery ratio in the Nillambe Oya watershed. Arc GIS 10.0 commercial software was used to calculate the soil loss from the catchment and daily sediment data were used to calculate the sediment load carried by the stream. Based on the above values the delivery ratio of the watershed was determined. The results indicated that the average soil loss was 436 tons/km2/year and the average sediment load was 63 tons/km2/year, which depicts that the Nillambe Oya catchment has good land-use with improved soil conservation measures compared to the upper Mahaweli watershed in general. The estimated sediment delivery ratio was only 0.14428 (14.43%). This was mainly due to sediment deposition in the areas with flat topography in the lowest part of the watershed. As a result, the carrying capacity of the river will be limited, leading to increased vulnerability of the catchment. Therefore, to restore catchments and river systems from soil erosion and sedimentation, proper ecosystem management tools must be implemented. 

Keywords: Catchment, Delivery Ratio, Sediment, Upper Mahaweli, USLE 

28 September 2021
2:30 pm - 3:00 pm - 28 September 2021

Afternoon Tea Break

28 September 2021
3:00 pm - 4:00 pm - 28 September 2021

RiverCo-Lab - Council of Mayors

Riversymposium - Room 1 - In-Person
Chair: TBA
28 September 2021
4:00 pm - 5:00 pm - 28 September 2021

Keynote Presentation

Riversymposium - Room 1 - In-Person
28 September 2021
5:00 pm - 8:00 pm - 28 September 2021

Welcome Function