Introduction

This practical links back to lecture 8 which was about greenhouse gas (GHG) emissions from freshwaters, and the role of anthropogenic (human) activity in driving these emissions. Today we will focus on reservoirs. Most reservoirs fall under the Intergovernmental Panel on Climate Change’s (IPCC) definition of flooded land: “ water bodies where human activities have caused changes in the amount of surface area covered by water, typically through water level regulation” . We will use Sweden as a case study, because it has created many reservoirs for hydropower.

Tip: Read through tasks 1-3 first to get an idea of what you will be doing – you might decide to combine tasks as you go along, rather than do them all sequentially. Full information on what is required for the assessment is at the end ofthe document.

Task 1

The first task today is to identify which waterbodies count as “flooded land” and therefore need to be    included in IPCC GHG inventories. Although sophisticated GIS techniques can be useful for things like     this, there is also value in simpler “off-the shelf” web applications. For this task, we will use Eniro Kartor (a Swedish mapping website).

Below are the names of twelve Swedish waterbodies.

First, you need to evaluate which of these count as “flooded land”, as defined in the introduction by the IPCC. Consider that the IPCC definition is qualitative, rather than quantitative, so you may have to make

some subjective decisions. To start the task:

1.    Go tohttps://kartor.eniro.se/

2.    How’s your Swedish? Click Flygfoto (“aerial photo”) at the top right.

3.    Click Sjökort mm (“charts etc)” to bring up a dropdown menu, then click Historiska flygfoton (“historical aerial photos”).

4.   You now have a line in the middle of the aerial imagery that you can drag left and right, to look at modern imagery and imagery from 1955-1967.

5.    In turn, copy and paste the names of each waterbody into the yellow search box at the top left. Compare the modern and old aerial imagery. This will allow you to see changes in waterbody    surface area, and you can decide which waterbodies count as “flooded land” according to your interpretation of the IPCC definition.

6.    Keep in mind that this approach will only allow you to see changes in surface area since 1955-

1967. If reservoirs were created, or dams built, before this date then you will not see changes in the aerial imagery. Consider other ways to check whether waterbodies are “flooded land” or not.

For task 1, present a list or table of the twelve waterbodies. For each waterbody, state whether you consider it to be flooded land or not, and why. This can be done concisely, eg: “this waterbody is flooded land because aerial imagery shows no waterbody previously existed here” or similar.

Task 2

In this task, we will map the extent of flooded land from task 1. We will continue the theme of using     simple “off-the shelf” web applications and use Google Earth. You can download Google Earth or use it online here:https://earth.google.com/web/

From task 1, take only the list of waterbodies that you have identified as flooded land. You need to         measure their surface area. To do this, copy and paste the waterbody names into Google Earth’s search function to find them. To map them:

1.    In the online version, click the ruler icon on the left hand side. You can then click on the map to delineate the outlines of your waterbodies.

2.    In the app version, cick the “map polygon” icon (next to the yellow pin icon at the top), and switch to “Measurements”, and then click on the map to delineate the outlines of your        waterbodies.

Either approach will allow you to calculate the surface area, in km2, of each waterbody in turn.

Tip: Sometimes Google Earth starts going 3D and changing the viewing angle. This can make mapping areas tricky. Pressing “R” will revert to a normal top-down view.

For task 2, present a table (must be neat, clear, and appropriately labelled) listing the individual       surface areas (in km2) of the waterbodies you have identified as flooded land. Also include the total area of flooded land when these are summed.

Task 3

Now we will use the information from task 2 to estimate methane (CH4 ) emissions from flooded land, using the 2019 IPCC Refinement report. A PDF is on the Canvas page, or you can download the report

here, the relevant chapter is 7 Wetlands:

https://www.ipcc-nggip.iges.or.jp/public/2019rf/vol4.html

For the purposes of this practical, we will assume that all the waterbodies you have identified as flooded land were created/modified > 20 years ago (in IPCC speak this is “Flooded Land remaining Flooded           Land”). To calculate your CH4  emissions you can use the IPCC emission factors (EFs) in Table 7.9. Note      that these are aggregated by climate zone. Sweden has a northern Boreal region and a southern Cool      Temperate region, and the border between these can be considered to run from Uppsala in the east to   Oslo in the west. To do this task:

1.    Categorise your list of flooded land into boreal waterbodies, and cool temperate waterbodies.

2.    Multiply the total surface area in each category by the appropriate EF, to calculate total CH4 emissions from your flooded land. Be careful here, you mapped surface area in km2, but the EF is in hectares (ha) so you will need to do a conversion (hint: how many ha are in one km2 ?).

For task 3, give your total CH4 emissions from boreal waterbodies and cool temperate waterbodies in tonnes CH4 year-1  (hint: how many kg in a tonne?). How do the magnitude of CH4 emissions vary between boreal and cool temperate zones on a per ha basis (i.e. the IPCC EFs) and when considering   total emissions scaled to all flooded land. What are the reasons for any differences between climate   zones? Here, we have only considered CH4 emissions, and ignored CO2 emissions – why have we done this (hint: the answer is in the IPCC report, and hinted at in the lecture slides too)? Use 200-400 words (excluding any references) to discuss and answer these questions.

ENVS214. Practical Three: Sediments, Reservoirs and GHGs – lab prac

For the lab component of this practical we will split into small groups of eight, and each group will get twenty minutes to do some measurements of freshwater carbon dioxide (CO2 ) emissions using            mesocosms (science speak for big buckets) in the lab.

One mesocosm is full of sediment and leaf litter – this represents a newly created reservoir, where large amounts of organic matter are inundated by flood waters. The second mesocosm is stocked with duckweed, to represent a reservoir where high inputs of nutrients have led to dominance of floating vegetation. In both, we will measure the chlorophyll concentration in µg/l using a Turner Designs FluoroSense.

We will measure the CO2 emissions using the floating chamber method. A small bucket is placed on the water surface and connected to a PP Systems EGM5 (a type of IRGA – infrared gas analyser). Air continuously circulates between the IRGA and the chamber. If CO2  is released from the surface of the    water then the CO2  concentration within the chamber will increase and the IRGA will show this (it measures CO2  in ppm – parts per million). If CO2  is consumed by the water/plants then the CO2 concentration on the IRGA will decrease. Float the chamber and record the CO2  concentration every 20 seconds – the change in CO2 should be approximately linear. You can continue the measurement for up to 240 seconds, or stop before then if a large change in CO2  has occurred. Measure CO2  emissions from both mesocosms, and make replicate measurements if time allows.

Once all groups have done the lab task, Mike will process the IRGA measurements to calculate the CO2 emissions, and then release the data on Canvas. In this way, those in the lab during the first session don’t get an unfair “headstart” on those in the lab during the second session.

For the lab task (task 4) use one graph (this must be neat, clear, and appropriately labelled) and 200-

400 words (excluding any references) to present, describe and interpret the CO2  results. This should include:

1.   A comparison of the two mesocosms (e.g. the result of a statistical test).

2.   What trophic class (nutrient status) the two mesocosms are (refer to Table 7.11 of the IPCC report).

3.   Considering (2), predict which mesocosm would have the higher CH4 emissions. Explain why (hint: the IPCC report and lecture slides should help).

Assessment Summary

Introduction (100-200 words). An introduction to freshwaters/reservoirs, sediments & GHGs. Include a short description of the methods.

Task 1 -  present a list or table of the twelve waterbodies. For each waterbody, state whether you consider it to be flooded land or not, and why. This can be done concisely, eg: “this waterbody is  flooded land because aerial imagery shows no waterbody previously existed here” or similar.

Task 2 - present a table (must be neat, clear, and appropriately labelled) listing the individual surface areas (in km2) of the waterbodies you have identified as flooded land. Also include the total area of flooded land when these are summed.