With summer fast approaching, ’tis the season for undertaking Stream Health Assessments. So, what are they, what do they look at, and why is this important on farm?
Undertaking Stream Health Assessments (SHA) on farm is a really valuable exercise that allows you to discover and monitor what is going on in your streams and rivers. From fish and kōura, to macroinvertebrates, algae and plants, there is a range of life living within our streams and rivers on farm. SHA’s provide a way to monitor stream health by assessing the conditions of your stream as well as looking a bit closer at the life which this water supports.
SHA’s are becoming a common monitoring tool for certification programmes and integrated farm planning, which allows farmers to record and understand changes over time, as well as providing food for thought when it comes to decision making around stream health and water quality on farm. Not only do SHA’s meet components of certification programmes, but SHA’s provide a great way to foster a closer relationship with the awa (stream/river) that flows through your farm.
What elements do we look at when undertaking a stream health assessment?
When undertaking a stream health assessment using the SHMAK (Stream Health Monitoring and Assessment Kit) method, there are a few key indicators that are monitored. These are:
- Site health check and land use
- Temperature
- Visual clarity
- Periphyton
- Macroinvertebrates
- Physical habitat visual assessment
Site Health Check and Land use
The site health check is a tick-box exercise which allows you to take note of key characteristics of the stream. This is important to undertake as it alerts if there are any unusual or concerning observations at the sampling site that may explain any results later in the assessment, or they may indicate a problem. It is also useful to compare if the site health check has changed since your last visit. The site health check assesses conditions related to smells, obstruction, margin or bank, appearance of the water, rate of flow, and the top of the surface water.
Temperature
The temperature of water is an important indicator as aquatic animals struggle to live in warm water (NIWA, 2019). Water above 22 Degrees Celsius can be stressful for many macroinvertebrates, with very few aquatic animals being able to survive above 30 Degrees Celsius. Cleared waterways with direct sunlight are at risk these temperatures, and it is common that waterways with not much shade will have fewer species of aquatic animals. Higher temperatures can also decreased the dissolved oxygen in water, harming organisms further. Riparian foliage and planting provides shade and refuge, enhancing stream health and the conditions for aquatic animals that call these waterways home.
Visual clarity
Visual clarity provides a measure of underwater visibility in streams and provides an indication of the concentrations of suspended particles within a waterway (NIWA, 2019).
Low visual clarity is an indicator of high levels of sediments in a stream, potentially from human disturbance, runoff and grazing. It is often accompanied by faecal contamination, nutrients, and other contaminants, so it may also indicate that levels of these contaminants are high (NIWA, 2019).
Low visual clarity can lead to:
- Restriction in sight for prey and predatory aquatic animals
- Decreased photosynthesis and plant cover from decreased light getting through the water to the stream bed
- Clogging of the gills of aquatic animals where high sedimentation is a key influence on clarity
- Submersion of habitat in sediment particles, decreasing habitat for smaller aquatic animals
Visual clarity is measured using a clarity tube (pictured below), which measures the distance through water that the human eye can see a black object.
Periphyton
Periphyton refers to communities of algae and cyanobacteria attached to the sediment surface or aquatic plants (NIWA, 2019). It plays an important role in streams as a food source for macroinvertebrates, however, too much periphyton can cause problems such as:
- Decreased habitat by smothering
- Decreased oxygen which impacts stream habitat
- Microcoleus can be toxic to dogs
Changes in periphyton cover over time can indicate changes in waterway health. Most small New Zealand streams have little obvious periphyton because they are naturally shaded and the periphyton is quickly eaten by benthic macroinvertebrates (NIWA, 2019).
NIWA (2019) state that blooms of nuisance periphyton are usually a symptom of a system that is stressed by factors such as:
- Nutrient enrichment
- High light from removal of bankside vegetation
- High temperatures that increase algal growth rates and stress some invertebrate grazers
Periphyton assessments are undertaken using the ‘stone method’ which involves estimating the percentage cover of periphyton on stones across the stream or river bed.
Macroinvertebrates
Benthic macroinvertebrates are animals that live at the bottom (benthic) of waterways (NIWA, 2019). They are big enough to be seen with the naked eye, but have no backbone. In streams, they are usually larval or immature stages of insects such as mayflies, damselflies, and caddisflies. As well as insects, there are also crustaceans such as kōura, snails, worms, and leeches.
Invertebrates found in streams will give you an indication of long term water health due to the knowledge of species environmental tolerances, rather than water testing which is a snapshot in time of current conditions (NIWA, 2019). Decreasing waterway health can lead to losses of some invertebrates, disrupting the food web, while some species will increase in abundance as water health decreases further, changing the systems away from natural conditions.
A tolerance score is assigned to the commonly found invertebrates, with a higher tolerance score meaning that the invertebrate is only found in healthy waterways as these invertebrates are more sensitive.
Macroinvertebrate assessments are undertaken using a kick net which gets a sample of macroinvertebrates from your stream. The different types of invertebrates are then identified and counted to reveal their abundance in the waterway. The tolerance scores of present macroinvertebrates are then added together, with a higher score indicating that the waterway is able to support more sensitive macroinverbrates.
Physical habitat visual assessment
Physical habitat refers to the entire stream environment including banks, bed, vegetation and habitat. Understanding the context of the wider stream habitat can provide insights into areas that could be worked on to improve stream habitat and health, and benefit the wider ecosystem.
This part of the stream health assessment is based off taking observations for 8 components each ranked from 8 (excellent) to 0 (poor), which are then combined to give an overall physical habitat score.
The 8 components observed for the physical habitat visual assessment are:
- Amount of deposited fine sediment
- Habitat for aquatic animals
- Flow types
- Bank stability and erosion
- Bank vegetation
- Riparian buffer
- Shade
- Channel alteration
It is important to note that a score of >55 (excellent) would be indicative of a natural stream, unimpacted by human activities and still fully surrounded by native forests. A farm monitoring site often will not look like this, not because of bad practice, but due to past clearing, grazing, and channel alterations. Instead, this score can provide insights into how actions could be put in place to further improve this score into the future, benefiting the stream ecosystem.
Some catchment groups around the country have access to stream health assessment kits, and in some regions like Otago, catchment advisors can help undertake stream health assessments on farm. We are always happy to help where we can, so if you need resources such as macroinvertebrate and periphyton ID guides, or recording sheets for your stream health assessment results, please do get in touch with us at lucy@thewholestory.co.nz