ENVSCI 201: Freshwater

Hydrology

The nature of how water flows within a system. How it enters, what it's doing, and how it exits.

Natural Flow Regime

The five components are:

• Magnitude
• Frequency
• Duration
• Timing
• Rate of Change

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The NFR affects the physicality of the stream (shape, complexity, etc). It affects the timing of biological processes (spawning). It helps connect bodies of water together and discourages invasions

Magnitude

The amount of discharge (flow) at any given time

Frequency

How often does a flow of a given size occur?

Duration

How long does a flow of a given size last?

Timing

What is the regularity of a flow with a given size? Are there any patterns? (seasonality)

Rate of Change

How quickly does the magnitude of the flow change?

Disturbances in Hydrology

Changes to the NFR that affects any of its five components. Charcaterised by:

• Magnitude (how big?)
• Duration (how long?)
• Frequency (how often?)
• Ptedictability (how reliable?)

Patterns of Disturbances: Pulse

A sudden increase then decrease

Patterns of Disturbances: Press

An increase that is then held at the same level

Patterns of Disturbances: Ramp

A gradual increase

Stream Chemistry

The physical conditions of the stream such as temperature, oxygen, and pH.

The nutrient content of the stream such as nitrogen and phosphorus.

Novel chrmicals and pollutants introduced into streams.

Stream Connectivity: Longitudinal

Looking at how the upstream is connected to and affects the downstream

Stream Connectivity: Terrestrial-Aquatic

How streams are linked to the terrestrial environment. Its riparian zone (off the banks) shows this connection.

The riparian zone affects the energy (light & resources) entring the stream, the habitat (channel form & debris), and chemisty of the stream. This also connects aquatic and terrestrial food webs.

Catchments also shows how land and streams are connected. What's happening on the land can and will end up in the stream/body of water.

Three Dimensioms to Streams

Longitudinally, this includes upstream and downstream.

Vertically, this includes the water in the channel to water beneath and in the sediment.

Laterally, this includes surrounding land such as the riparian zone.

Stream Complexity

How diverse the stream is in terms of biodiversity, shape, structure, conditions, and so on.

Biodiverse in the sense of different flora and fauna species. Variable in the sense of flow and sediment variability.

The more complex a stream is, the higher its capacity to hold and support different species.

Stream Health

Measuring stream health looks at the stream's hydrology, chemistry, connectivity, and complexity.

There is also a cultural health aspect which is more anthropogenic based (eg. incorporating mātauranga māori).

An example of a metric is the macroinvertebrate community index which takes account the number of species present and each species' ability to tolerate pollutants. The higher the score, the cleaner the water

Urban Stream Syndrome

Describes the consistently observed ecological degradation of streams draining urban land.

How the precense of urban landscapes affect and changes the hydrology, connectivity, chemistry, and complexity of streams.

Basic Hydrology Cycle

The main input is precipitation. The main outputs are runoff and evapotranspiration. There's many fluxes, the movement of water, between other bodies of water, the atmosphere, the biosphere, and so on.

Infiltration

The flux of water from runoff and water on the ground moving underground

Overland Flow

The flux of water accross the land either as rainfall (runoff) or flood water from streams

Discharge to Surface

The flux of water underground leaching into bodies of water

Runoff

When precipitation falls onto and flows over land. Typically most will infiltrate into the ground under natural permeable landscapes.

However, in urban systems, the impermeable surfaces prevent runoff from infiltrating. There are some permeable spaces in urban areas like green spaces and gardens.

Urban Stream Syndrome Effects on Hydrology

Higher rates of runoff with almost no rates of infiltration and some evapotranspiration.

All the excess runoff typically flows into and overloads nearby streams. Sometimes the runoff is collected and goes through subsurface routing into streams.

All of this means a higher magnitude and faster rate of change of discharge. This leads to situations such as floods and the faster high intensity water also causes more erosion.

• Higher magnitudes of flow

• More frequency of overland and erosive flow

• Less lag time between peak flows

• Higher and lower rises and falls of storm hydrograph

Baseflow magnitude (magnitude when there's no rain) tends to be inconsistent as well.

Urban Stream Syndrome Effects on Morphology

The physicality of the streams are modified to better suit human needs. Channels are straightened, made wider and deeper, and less complex. The flashier flows also tends to make more scour at the bottom. They are also typically burried and put underground and diverted elsewhere.

The levels of sediments entering also tends change too, however more inconsistently. Initially with all the developments, sediments will skyrocket but after things settle down, there tends to be little to no sediments.

Naturally streams would have diverse intact vegetation (riparian zone), natural channels with curves, and morphology to support variable flows, pool sizes, sediments, and ripples.

• Wider channels

• Deeper streams

• More scour

• Less complexity

Urban Stream Syndrome Effects on Chemistry

There is a higher inputs of natural sediments and novel pollutants typically being carried by runoff the goes over urban landscapes. For example, road salinisation for snow results with higher salinisation in bodies of water.

Streams are being overloaded with nutrients such as nitrogen and phosphorus typically from argicultural practises (fertilise-use and animals). Some may even come from urban runoff from the combustion nitric oxide.

Temperatures are higher due to the urban heat island effect, the lack of riparian shading, and hot incoming runoff.

Similarly, sediments within the stream also tends to be inconsistent, depending on the stages of development, policies invovled, and so on.

Urban Heat Island Effect

The phenomenon in which urban areas are warmer than the surrounding countryside due to pavement, dark surfaces, closed-in spaces, and high energy use

Agriculture Development on Streams

It involves a lot of changes such as land disturbances, water diversion, nutrient enrichment, and animal stocking

Agriculture & Land Disturbances

The development of agriculture typically means the removal of streams' riparian zones.

This means changes to shading, detritus/energy incoming, and sediments within the stream (typically becoming homogenised).

The woody debris that is taken away is important for shaping the physical habitat & channel as well as allows for variable flow.

Channels tend to be alrtered, straightened, or even may be diverted. This also includes modification of the floodplain.

Agriculture & Hydrology: Irrigation

Typically, water from streams are diverted and used as irrigation for crop land. Water is typically harvested, stored, and distributed. Or, they may pump groundwater using wells. All of which means less flow due to less water being in streams.

At times, tile drains are used to quickly collect terrestrial surface water, pumped through pipes, and then drained into nearby streams

Agriculture & Hydrology: Groundwater Pumping

Excessive groundwater pumping also lowers the water table. As we dig wells and pump, the water table lowers and then we'd have to dig even lower. It can reach a point where instead of groundwater leaching into streams, the stream leaches into the ground instead (loses input of water).

Environmental Flow

Defined as the amount of water input required over tiem to maintain river health in a particular state

Agriculture & Nutrient Enrichment: Nitrogen

Fertiliser-use and nearby animals tend to increase the amount of nitrogen ending in streams. Nitrogen can be swept into streams through runoff or leached into the ground and eventually into streams.

Excessive nitrogen levels can kill species. However, eutrophication is the main issue caused with nutrient enrichment.

Agriculture & Nutrient Enrichment: Phosphorus

There is typically also phosphorus in fertilisers that may end up in streams too. Most of the phosphorus comes from excess erosion due to higher magnitude flows. Phosphorus can also lead to eutrophication.

When lakes become anoxic, phosphorus is released and ressurects algal blooms. In typical oxygenated conditions, phosphates react with iron to create sediments and sink, making it unavailable for algae.

Eutrophication

Also known as algal blooms, is when algae populations explode due to excess nutrients.

It greatly disrupts aquatic ecosystems for various reasons:

• It blocks out the sun, preventing other aquatic plants from photosynthesising
• As algae die and sink, they undergo aerobic decomposition. Excess algae leads to anoxic conditions for waters below.
• These anoxic conditions greatly impact aquatic ecosystems, food webs, and so on.
• Temperatures will also greatly decrease as you go down. These waters below don't mix with waters above

Bioindicators/Biomonitoring

The process by which orgabisms and or biological processes are used to measure the health of the environment over time and space

Organisms are like the bloodline of ecosystems. The tend to intergrate stressord, complex processes, and effects over time. So this shows us a timeline of changes rather than just one snapshot

Quantifying Ecological Responses: Structure

We can look at:

• The density of individuals or total biomass
• Specied richness and abundance

Quantifying Ecological Responses: Function

We can look at:

• Metabolic rates (primary production, respiration)
• Rates of decomposition
• Rates of nutrient cycling

Macroinvertebrates

Organisms without backbones, which are visible to the eye without the aid of a microscope. Insects make up a big chunk of macroinvertebrates. They're commonly used as a way to determine ecological health.

Why Macroinvertebrates as Bioindicators

• They're ubiquitous, being found everywhere
• There's a variery of taxa that offers a spectrum of responses
• They're sedentary, spending their life in one place
• They have relatively long life cycles
• They're to identify and sample
• We have extensive well-developef data analyses for them

Structural Indicators

1. Abundance of each macroinvertebrate species
2. Richness of species, typically using a diversity index

Indicator Taxa

The precense and abundance of specific species may tell us the health of a stream.

An example is the MCI which gives each macroinvertebrate a pollution tolerance score. The abundance of some macroinvertebrates (eg. more pollution tolerant) tells us how polluted the waters is.

Community Structure

Observing the sort of taxa we have, whether it's more sensitive or tolerant taxa

Urban & Agricultural Land on Ecological Health of Streams

Urbanisation & agricultural development tends to decrease ecological indices.

It is dependent on how development goes about.

• Amount of impervious area
• Whether riaprian zones and corridord exist
• Where the land is used relative to streams
• How much total catchment impervious area

The riparian zone is crucial for streams as it provides shading, an input of energy, as well as habitats.

Macroinvertebrates tend to be negatively affrctef (consisted reduce diversity, richness, etc)
Algae don't have a clear or consistent reaction. Their response is on shorter time scales and don't integrate effects as well as long-lived taxa.
Fish also have similar mixed results. A lot of which has to do with historical agricultural practises.

Index of Biotic Integrity

Uses multiple measures and integrates it into one single metric. It looks at richness, habitats, natives/invasives, abundance, and many more

Shannon-Wiener Index

H' = -(n SUM i = 1 of pi × ln(pi))

It is the absolute value of the sum of the proportion of each species multiplied by the natural log of its proportion.

The higher the index, the more biodiverse the area is.

MCI

MCI = average taxa score × 20

Higher values indicate clearer waters. Having more sensitive taxa means that the water is clean enough to support them.

Hilsenhoff Biotic Index

HBI = (n SUM i = 1 of Ti × Ni)/x

T = Tolerance value of each HBI species
N = Number of individuals of each HBI species
x = Total number of individuals of HBI species

The higher the score, the more polluted the water is. High scores indicate a lot of pollution tolerant species, indicating that the waters is polluted.

Historical Land Use & Streams

The historical land use of the land catchment around a stream can tell us many things about its health present day.

Typically, catchment areas that were used as farmland, abandoned, and reestablished had more erosion due to the previous agricultural practises. This erosion also caused more fine sediments to be present within the stream.

Non-Linear Patterns of Response to Urbanisation

A lot of the responses to urbanisation are non-linear. A lot of them show up as curves where it may go up a bit and then start going down.

These patterns has implications on how far we can push a system before a significant change occurs. It also allows us to more easily define limits of urbanisation too.

Ecosystem Functions

The various processes that are required to keep an ecosystem going. This includes its:

• Energy inputs & outputs, typically photosynthesis and respiration.
• Decomposition, the breakdown of organic matter typically done by microbes (bacteria), fungi, and etc
• Nutrient cycling within a system, how nutrients are taken in, how it's limited, and how it flows through a system

Ecosystem Functions: Energy

Typically, when looking at the energy flow within a system, we look at photosynthesis and respiration.

One way to do this is by measuring and looking at the biochemical oxygen demand of a stream. This works for both photosynthesis and respiration as photosynthesis would be the addition of oxygen into a system while respiration would be the removal.

• Measuring the oxygen decline of a sample can also tell us how polluted the waters are.

Gross Primary Production (GPP)

The total autotrophic production of an ecosystem. All of the energy produced by an ecosystem, whether through photosynthesis or chemosynthesis.

It is most influenced by the light and nutrient inputs of an ecosystem. Temperature also tends to increase GPP.

Ecosystem Respiration (R)

The energy consumed by both autotrophs and heterotrophs within an ecosystem.

Many different factors may increase or decrease it. Mainly, it is affected by the nutrient and organic matter input as well as hydrology.

Net Ecosystem Production (NEP)

The difference between GPP and R, the net amount of energy left over after autrophic and heterotrophic use.

NEP tends to be negative and that's okay. This suggests that there is also an outside input of energy besides photosynthesis.

Riparian Zones & Ecosystem Functions: Energy

Riparian zones are extremely important in the energy cycles of streams. Riparian zones play a role in energy input as any detritus that falls in (woody debris, leaves, etc) can be used as organic matter for respiration.

Typically, many streams need their riparian zones because the stream's producers don't produce enough energy to support the entire ecosystem.

Ecosystem Functions: How do we Measure Energy?

There are two ways we measure energy, using a chamber method or an open channel method.

Measuring Energy: Chamber Method

When using a chamber method, we use'd look at the oxygen change over time between a dark bottle and a light bottle of water samples.

The dark bottle gives us only the respiration rate as photosynthesis isn't possible for that water sample. While the light bottle gives us the photosynthesis and respiration rate.

So, figuring out the energy is just the difference between the two

Measuring Energy: Open Channel Method

Two different points of a stream are measured, one upstream and one downstream, to measure the change in oxygen.

There is alsos a change in oxygen from upstream to downstream, typically a negative change.

As the water flows between the two points, the producers photosynthesise, organisms respire, and reaeration also occurs.

Urban & Agricultural Development on Ecological Functions: Energy

Overall, urbanisation and agriculture tends to greatly increase the GPP of a stream. This is due to many factors inclduing:

• Less shading due to removal of riparian zone (more light)
• Nutrient inputs from runoff, fertilisers, and so on (more nutrients)
• Higher temperatures tend to also make photosynthetic rates faster

However, the respiration of the stream tends to stay the same/similar when compared to natural streams.

But, these streams tend to also have not as negative NEP. As mentioned before, many streams rely on the riparian zone as an extra input of energy. The lack of riparian zones mean that the organisms within these streams need to rely more on the stream's producers.

Urban and agricultural streams tend to also have more similar GPP production rates while natural streams are more variable.

All in all, this causes the diurnal patterns of dissolved oxygen within the streams to be more intense

Algal Blooms & Ecosystem Functions: Energy

Algal blooms can drastically change the amount of dissolved oxygem within a stream. Typically, it'd increased the magnitude of the diurnal pattern of dissolved oxygen throughout the day.

This means that throughout the day, it'll get extremely high and low dissolved oxygen levels. Extremely low dissolved oxygen levels can be very toxic for the organisms within the stream.

Typically for all streams, dissolved oxygen is the highest during the day (mid-day, morning, afternoon, etc) because the sun is out. It is lowest typically during the night (mostly pre-dawn, midnight, etc) as only respiration occurs.

Ecosystem Functions: Decomposition

Typically, we'd see any detritus falling into the stream being decomposed by microbes, bacteria, and fungi into fine particulate organic matter (FPOM).

The rate of decomposition is affected by the microbes present, nutrients within the stream, the hydrology of the stream, and also leaf shredding invertebrates.

Urban & Agricultural Development on Ecological Functions: Decomposition

The rates of leaf decomposition tends to get faster with more urban and agricultural developments.

This is due to how:

• There tends to be increased nutrient inputs that support decomposers

• Less varied flows, allowing for easier decomposition

• Higher temperatures which speeds up decomposer activities (microbial)

• Typically more microbial communities are present too.

However, this trend isn't linear. Typically, with extreme amounts of urbanisation, decomposition rates start to decline.

• Rates increase initially due to how the added nutrients, higher temperatures, and so on aren’t at such an impactful level yet

Measuring Decomposition

It’s as easy as measuring the mass of a container/bag of leaves in a stream over time. This would give us a graph where it initially is decomposed quickly but slows down overtime.

The natural log of this gives us the slope, also known as the breakdown rate

Paradox of Enrichment

The hypothesis that applying some sort of stress can initially increase and stimulate the rate of something. But, as we apply more and more stress, it’ll get to a point where the system can collapse.

• This is seen in decomposition rates

Restoration Goals

Typically, most goals focus on biodiversity of the stream. Then it is followed by channel stability, riparian habitat, in-stream habitat, and water quality.

Restoration Methods

Most methods aim at modify the stream’s morphology and hydrology. Others may focus on riparian restoration. Typically these efforts are on a smaller scale rather than a larger scale.

Riparian Zone Importance

Riparian zones act as a buffer zone for incoming runoff water. They help to regulate the temperatures, sediments, pollutants, and energy of incoming runoff. They also provide an energy input with its detritus as well as provide habitats.

Riparian reconstruction is typically one method for restoration. The width and length of these efforts may have implications on how effective they are, but we are lacking data as most riparian reconstructions are done on a smaller scale (which doesn’t show as much change).

Riparian Replanting

Typically done in urban streams, when the riparian zone is restored by replating specific plants. Successfully doing this is supposed to bring all the benefits that comes with having a riparian zone (energy input, shading, regulation, filteration, etc)

However, it’s effectiveness depends on how the land is actually used around it. The presence of subsurface pipings that directly flow water into stream, going past the riparian zone, completely misses the point of having a riparian zone.

Riparing Fencing

Typically used in agricultural streams where the riparian zone is fenced off from the stock animals. Riparian replanting also tends to occur to restore the riparian zone.

This has the same benefits and limitations as the riparian replanting of urban streams. It also has the added benefits of preventing erosion and nutrient inputs as the fence prevents animals from going near the stream and disturbing the soils.

Ghost of Land Use Past

As talked about before, the effectiveness of these restoration efforts heaving rely on the historical land use of the stream and surrounding area. For example, historical agricultural land-use may mean more sediments in streams which may create problems during restoration efforts and or to the ecological health of the stream

Typically, these efforts tend to improve ecological health somewhat. But we are severely lacking data to state a clear relationship.

Rain Gardens

Green areas that allow for some runoff to infiltrate into the ground instead of being directed into streams through subsurface piping. It uses the concept of bioretention and act as water sinks essentially.

They help to filter incoming particles from runoff, absorb incoming contaminants, increase infiltration into the ground, and also delay stormwater pulses. They tend to have overflow inlets that may directly source runoff into streams when rainfall is too intense

Man-made Habitats/Streams

Man-made habitats or streams are also made, typically with a lot of physical land modification and dredging. These efforts are aimed at creating suitable habitats and streams for organisms to come in and colonise.

Daylighting

It’s a movement of resurfacing the previous grounded and piped streams. A lot of streams are piped and placed underground. This also applies the same concept of create habitat but instead of new habitat, it’s the restoration of old ones.

These tend to be extremely expensive and time consuming. The effectiveness of these efforts also depends on the goals of daylighting, whether it is more for the cultural aspect or for the ecological component

Field of Dream Hypothesis

It states that if habitat is made (whether new or restored), organisms will come back, colonise, and settle within it. Whether or not organisms comes back to a restored area depends on that area’s connectivity with other already established areas.

Organisms need to be able to successfully disperse from established areas to these newly restored areas, or else they just won’t come.

Nitrogen Cycle in Agricultural Lands

The normal nitrogen cycle is heaving modified and disturbed when agricultural practises are in play.

There is an extra input of nitrogen in the soils (typically from fertilsers and animal waste in the form of ammonium). The ammonium in the soil tends to stick to the soil as it is positively charged. Any unused ammonium is converted into nitrates through nitrification. Nitrates are negatively charged and are therefore easily leached out. The excess ammonium typically means excess nitrates that end up in bodies of water.

Dinitrification is then the final step that converts nitrates back into nitrogen gases.

Nitrification Inhibitors

Work by blocking the nitrification of excess ammonium and mineralisation of animal waste. While it proved to be effective, it had implications as there were questions whether it could work on a larger scale and its possible threats in ending up in dairy/food products.

Two Stage Ditch

When the surrounding floodplain is modified so that there is a step down right before the stream, creating a minifloodplain (typically with riparian plants as well).This is done to help slow down the incoming runoff as well allow the land to better retain various nutrients and contaminants.

It also created anoxic and saturated conditions that allowed for more denitrification, preventing more nitrates from entering the stream.

Scale of Solutions vs. Scale of Problems

Typically, the actual problems that we face are a lot larger than the solutions we apply. Streams are huge and can stretch for kilometres, going past through many different land-uses, have many different disturbances along the way, and so on and so forth.

Typically, we tackle restoration on a lot smaller scale such as on a local scale where we address the stream’s health in a small region. However, there have been efforts to focus restoration on entire catachments as well.