Enviro water test

What are the key components of a healthy freshwater system?  

• Habitat compexity 

• Hydrology (including natural flow regime and disturbance)  

• Chemistry  

• Connectivity  

Can you explain what each is and why it matters? 

• Hydrology encompases the movement and distrobution of water throughout a system. A key part of hydrology is the natural flow regime which is the flow of water overtime, how it evolves and changes naturally to support ecological integrity and the supply of nutrients. Flow is characterised into magnitude; the amount of flow at a given time, frequency; how often these flows occur, duration; how long the flows go on for,timing; how often and regular are these flows which links to seasonality, rate of change; how quickly a flow magnitude changes from big to small. Disturbance is also a key factor of hydrology and alters how likely organisms are able to survive in such environments  

• Chemistry encompases the chemical nature of streams incluting nutrient avalability, energy from sunlight which is used for GPP gross primary production and is crucial in the foundation of nutrient cycling and aquatic food webs. Nutrients liike nitrogen and phosphurus are also important to chemistry but have the ability to harm ecosystems when levels are too hig, temperature is also involved in chemistry and can effect and organisms livelyhood in the environments. Pollutants are a key part of chemistry  and the function of freshwater ecosystems and provide a measure for novel chemicals and anthropogenic stressors. 

• Connectivity relates to the linking of different parts of streams as catchments can be quite large. This component is crucial in unstream and downstream flow patterns and is characterised by longitudinal and latitudinal connectivity.  this allows the flow of nutriens and organisms from and to different parts of streams. It includes floodplain interactions and groundwater. Riparian connectivity also plays an important role in energy input, enery availability and chemisty. 

• Habitat compexity creates greater oppertunity for biodiversity. It reffers to the variety of physical structures in streams such as substrate, debris/debris dams and flow variation. Greater habtiat complexity provides greater living conditions for organisms and supports ecosystem stability  

What is the ‘urban stream syndrome’? 

The urban stream syndrome is the concept of when we build cities, there are patterns in areas with urbanisation that effect freshwater systems and hydrology. It encompasses a common set of negative changes resultant from urbanisation.  

What are fairly consistent changes in streams associated with urbanization? 

Such changes observed in streams due to urbanisation include increased runoff from impervious surfaces. This alters flow patterns in streams as precipitation causes runoff over impervious surfaces carrying harmful chemicals into streams, increasing erosive flows. This is because runoff increases and infiltration through soil decreases. This increases peak flows, magnitude and rate of change in them. Runoff also causes pollution from industrial discharge, chemicals and wastewater in streams which degrades water quality, causes algal blooms and oxygen depletion. As a result we see biodiverity loss and distrupted nutrient cycling. Another key promplem is the loss of riparian connectivity and vegitation. Increased temperature due to hot impervious surfaces and runoff aswell as loss of riparian shading (solar heating)  

What causes those changes? 

• Subsurface routing which effects deep infiltration, water exchange and shallow infiltration  

• Interrupts flows by creating pipes and manmade drainage systems  

 How does agriculture modify the physical nature of freshwater systems? 

• Increased sediment loads and clogging of initial habitat  

• Increased soil disturbances leads to erosion  

• Changes to channel Straitening of streams for agricultural land, creating new streams disturbance from digging to try avoid flooding on agricultural landscapes  

• Changes hydrology from irrigation and draining groundwater systems  

• Tile drains which drain water from surface into underground pipes pumped out into streams taking nutrient pollutants directly to streams  

Agriculture significantly modifies the physical nature of freshwater systems by altering hydrology, stream structure, and sediment dynamics. Drainage modifications, such as tile drainage and ditching, speed up water movement, reducing groundwater recharge and increasing stream flashiness, which can lead to more frequent flooding. Channelization and straightening of streams for irrigation and drainage efficiency disrupt natural meanders, reducing habitat complexity and increasing erosion. Deforestation and riparian vegetation removal expose streambanks to erosion, leading to excessive sedimentation that degrades water quality and smothers aquatic habitats. 

How does agriculture modify the chemical conditions of freshwaters? 

Agriculture modifies chemical conditions of freshwater by increasing nutrient pollution input and removing riparian vegetation. This increases nutrient runoff and contamination from fertilisers. Additionally, sediment loads from agricultural runoff can alter the chemical composition of streams and oxygen availability.  

• Increased irrigation and runoff  

• Algae blooms  

• Algae die and bacteria break them down using oxygen and causing eutophication  

What are some common ways to measure ‘ecological health’? 

• Biomonitoring MCI ect  

• Water quality testing 

• Habitat assesment  

• Algal monitoring  

• Connectivity and hydrology  

Why do we need more than one way to measure health? 

It is important to measure health in multiple ways as indicators can relate to different areas of ecological function, such as pollution and chemistry, biodiversity, hydrology and nature of flows.  this links to the complexity of natural aquatic systems which require different insights of what health looks like. When using a diverse range of techniques, subtle changes and stressors can be detected easily with both long and short term perspectives.  

What are common patterns in ecological response to increasing urban and agricultural land use? 

Due to habitat distruption, pollution, increased flows, sedimentation and erosion  

• Loss of biodiversity: Sensitive species decline as pollution, habitat degradation, and hydrological changes favor more tolerant species. Urban and agricultural streams often shift from diverse ecosystems to ones dominated by hardy, generalist species. 

• Shifts in primary production:  Excess nutrients from fertilizers and urban runoff promote harmful algal blooms, leading to lower oxygen levels and shifts in aquatic plant and microbial communities. 

• Altered nutrient cycling: Increased nitrogen and phosphorus inputs accelerate eutrophication, disrupting natural nutrient processing and leading to long-term water quality issues. 

What are typical responses of ecological function to urban and agricultural land use? 

Reduced organic matter processing: lack of debris and microbial activity to breakdown material and support food webs (sedimentation| peak flows)  

Higher primary production & excessive respiration from algal blooms  

Net ecosystem production decreases or becomes negative more organic matter consumed than produced  

 What are ‘non-linear’ responses and why are they important?  

Nonlinear responses to urbanisations effects on freshwater systems is underscored by the idea that not all stressors result in immediate reduced health. Often responses to change like removal/change in riparian cover can cause a n increase in biological activity (chemical cycling and energy production from available sunlight) before dropping long term and proving negative responses. Non-linear responses also indicate habitat complexity and variability. Another example of non-linear responses highlights the disproportionate responses to disturbance; gradual pollution may initially stimulate activities in ecosystems however when more is added overtime the process can collapse. This is important to understand responses and develop proactive management techniques.  

Can you explain 2 different measures of ecological function (what they measure, what drives them, how they respond to human influence)? 

Ecosystem metabolism (chmaber methods) measures the balance between primary production (photosynthesis) and respiration in a freshwater system, indicating how energy flows and how efficiently the system produces and consumes organic matter. It is driven by factors such as sunlight availability, nutrient levels, organic matter inputs, and microbial activity. High levels of plant and algal growth increase primary production, while microbial and animal respiration consumes oxygen. Human activities like agricultural runoff and urbanization can disrupt metabolism by increasing nutrient loads, which can overstimulate algal growth, leading to oxygen depletion and habitat degradation.  ecosystem metabolism is measured using dissolved oxygen sensors, which track changes in oxygen levels over time. By analyzing oxygen production during the day (photosynthesis) and oxygen consumption at night (respiration), scientists can estimate the system’s overall metabolic balance. 

Nutrient cycling refers to the movement and transformation of essential elements like nitrogen and phosphorus within an ecosystem, which supports plant growth, microbial activity, and overall water quality. This process is driven by biological uptake, decomposition, sediment interactions, and hydrological transport. In healthy freshwater systems, nutrients are efficiently recycled, preventing excess buildup and supporting a balanced ecosystem. However, human activities such as fertilizer use and wastewater discharge introduce excess nutrients, disrupting this cycle and leading to problems like eutrophication and oxygen depletion. Scientists measure nutrient cycling through water sampling and stable isotope tracing, which track how nutrients move through the ecosystem. Additionally, measuring denitrification rates (the microbial process that removes nitrogen from water) helps assess how effectively a system processes excess nutrients. 

What are typical goals and approaches to restoring freshwater systems? 

Goals and approaches to freshwater systems include, restoring biodiversity, water quality, channel stability, riparian habitats and instream habitats. Means of achieving these goals involve channel hydromorphic (daylighting, floodplains ), in stream hydromorphic (dredging) , riparian restoration and watershed action (rain gardens). 

Can you describe specific approaches to restoring urban streams?  What are they supposed to fix? 

Current approaches to restoring urban streams include, dredging- a process in which sediments are removed from stream systems to restore the structural habitat and allow new nutrient rich sediments to regenerate and support ecology. riparian planting with increases natural shading, inputs of detritus which improve nutrient availability, chemical cycling, the nature of flow and reduce pollutant runoff through sediment/soil uptake. Daylighting, a process where underground urban stream systems are dug up and brought to the surface as their original stream form, this helps connect people to water, increase input from leaves and wood and bring energy from sunlight into streams where organisms could possibly recolonise. Finally,  installing raingardens which focuses on infiltrating stormwater runoff through soils, filtering out contaminants as water infiltrates to streams, overflow pipes takes water to stormwater retention basins delaying runoff into streams and disturbance to NFR . Each attempt to reconnect or restore urban streams to their natural ecology.  

Can you describe specific approaches to restoring agricultural streams?  What are they supposed to fix? 

Current approaches to restoring agricultural streams include riparian fencing and planting which aims to reduce the amount of pollution contaminating streams from fertilizer and agricultural runoff. It also aims to increase natural shading, input of leaves, wood and detritus into streams, increasing habitat complexity and flow paths to support life. Another approach is reconnecting floodplains to manage excess runoff which allows excess water to flow overland,  reducing peak flows, filtering pollutants, and promoting denitrification through sediment and phosphorus retention.  

What are common problems in current approaches to restoration? 

Current approaches to restoration of freshwater systems are underscored by a lack of clear success criteria, poor understanding of long-lasting benefits to ecological health and the "ghost of land uses past" which links to sediment composition and nutrient availability from urbanisation of agriculture overtime interrupting the restoration of ecological health in streams.  Without completely restoring longitudinal connectivity in streams and natural flow mechanisms, biodiversity struggles to regenerate with many flow paths still obstructing the natural hydrology of such streams.  

• Cannot focus on large enough catchment due to time and money to make a definite impact