Land use – impacts on waterways

Discover some of the issues involving land use and water quality.

We have modified the land to create cities, businesses, farms, roads and other infrastructure. These modifications often make our lives safer and more comfortable. They allow us to produce food and other goods and services. However, land use can have impacts on our waterways.

To use this interactive, move your mouse or finger over any of the labelled boxes and click to obtain more information.

Transcript

Natural land cover

Native forests allow water to infiltrate naturally. Water is taken up by the trees and then released slowly, reducing the risk of flooding. The roots of trees stabilise stream banks and provide good hiding places for insects and fish. Shade from the trees keeps the water cool for animals in the stream. The insects, leaves and logs falling into the water provide food and homes for stream life. Leaves also fall on the ground and build up a litter layer, which is a good filter for water running off the land – slowing it down and settling out the sediment before it gets to the stream. The water that enters streams from native forests is generally cool, clear and safe for swimming and requires less treatment for drinking.

It is helpful to retain or restore tree cover to stream banks and headwaters to protect soil, regulate water flow, provide good habitat and buffer run-off from the land.

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Acknowledgement: The University of Waikato Te Whare Wānanga o Waikato and Waikato Regional Council

Erosion

Erosion has a number of causes but the impact is the same – precious soil enters a waterway and is eventually washed out to sea. Manaaki Whenua – Landcare Research reports that New Zealand loses 192 million tonnes of soil each year – the equivalent of 400,000 dump trucks of soil every week!

Bare soil exposed by roadworks, subdivisions, cultivation, overgrazing, slips on steep land or stream bank trampling can be washed into streams and rivers during rain.

This reduces the clarity of waterways, impacting on the plants and animals. High sediment levels will also increase the amount of treatment required for drinking supply.

Roadworks and other activities that disturb the soil usually require an erosion and sediment control plan, including proposed revegetation techniques.

There are practices farmers and growers can follow. Steep areas can be retired from grazing and planted in a timber crop or left to regenerate into native bush. Crops should be planted in rows across a slope rather than down, with cultivation kept to a minimum. Crop stubble should be left on paddocks and a cover crop planted when land is left fallow.

Acknowledgement: Photo by Astrid VanMeeuwen-Dijkgraaf, DOC. Crown Copyright 2004.

Stock access to waterways

There are a number of issues regarding stock having access to waterways. Animals trample the banks and remove vegetation, leading to erosion. They stir up the stream beds, which affects stream habitats. Animal faeces contain harmful bacteria such as E. coli.

Fencing streams not only protects the waterways, it protects stock from becoming injured or dying if they get stuck in boggy areas. Riparian planting filters out sediment, nutrients and faeces from surface run-off and creates habitats for creatures living on the land and in the stream.

Waikato Regional Council monitors riparian fencing to assess stock access to waterways. Farmers who take water from a stream on their property need to have a riparian management plan and are required to fence the stream and progressively plant the stream banks.

The Sustainable Dairying Water Accord is a set of national good-management practices that guide farmers to quality riparian management. It reported in 2019 that significant progress has been made to exclude stock from waterways across New Zealand.

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Acknowledgement: The University of Waikato Te Whare Wānanga o Waikato and Waikato Regional Council

Managing farm effluent

Effluent is the liquid waste created when milking sheds and animal yards are cleaned with water. It is a valuable resource – using effluent to irrigate the land reuses both nutrients and water. As effluent filters through the soil, physical, chemical and biological processes remove harmful bacteria.

There are regulations about how effluent is stored, managed and used. Effluent cannot be discharged into streams or rivers. Care must be taken when effluent is irrigated onto the land so that it does not contaminate groundwater. Care must also be taken during wet weather to avoid surface ponding and run-off into streams and rivers.

Having adequate storage ponds means farmers can choose when to irrigate. This makes best use of the water and nutrients during dry weather and/or plant growth and reduces the need to irrigate in wet weather.

Riparian planting on stream edges creates a natural filter for run-off water and sediment.

The Sustainable Dairying Water Accord is a set of national good-management practices that guide farmers to quality riparian management. It reported in 2019 that significant progress has been made with effluent planning and sustainable actions across New Zealand.

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Acknowledgement: The University of Waikato Te Whare Wānanga o Waikato and Waikato Regional Council

Water use

New Zealand has an abundance of freshwater, but water is not something we should take for granted. When we take too much water, our streams and rivers are affected. Water levels and flow patterns change, water temperatures rise and algal blooms become a problem. This can affect the cultural value of the waterway as a food source. It also affects the life essence (mauri) of the waterway.

Groundwater is also affected when we take too much water. As the water level in an aquifer drops, water flow to springs, rivers and streams also drops. Removing too much water from coastal aquifers may allow saltwater to enter the aquifer and make the water unusable.

As cities grow and horticulture and farming intensify, greater pressure is put on our water resources. Regional councils require resource consents to take water. They also measure water allocations for purposes such as town and city drinking water supplies, farms and manufacturing plants.

We should all take responsibility for water conservation. By doing so, we help to protect our waterways, save electricity and reduce the cost of drinking water and wastewater treatment.

Acknowledgement: 123RF Limited

Intensification

Farming is a way of life in New Zealand – about half the country’s land is used for primary production. The need to produce more food to feed a growing population and the reduction of productive land to be used for housing creates the issue of intensification.

To achieve higher agricultural and horticultural production (intensification), farmers and growers often increase stock numbers, take additional water for irrigation, and increase the use of fertilisers and pesticides. Fertilisers and pesticides need careful management to ensure they stay in place and are not carried away by leaching, run-off or erosion.

Increased stock numbers also leads to more urine deposits in paddocks. The urine has more nitrogen than the pasture plants can take up, so the excess nitrogen leaches into groundwater and eventually makes its way into surface water such as streams and lakes.

Riparian and other types of planting help to filter sediment and nutrients from entering into waterways.

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Acknowledgement: The University of Waikato Te Whare Wānanga o Waikato

Sealed surfaces

Sealed surfaces such as roads, buildings and carparks prevent rainwater from filtering into the ground. Instead, rainwater runs off into the street and enters stormwater drains, carrying with it any pollutants, such as oil, fuel and rubbish which directly flows unfiltered into nearby streams and rivers. Washing cars on sealed surfaces washes pollutants directly into stormwater drains and into waterways.

We can reduce the sealed surfaces around us by using materials that will allow water to filter naturally such as gravel, bark, shells or pavers with gaps between them, or by maintaining grassy or treed areas. This is becoming even more important as infill housing creates hard surfaces where lawns and gardens once existed. We can also make informed choices about what chemicals we use and dispose of close to and in stormwater drains or on grassed areas such as lawns and to never drop litter outside.

Acknowledgement: Boffa Miskell

Land drainage and flood protection

Landowners face a conundrum – we need water for everyday purposes, but we don’t want too much of it. Farmland is often crisscrossed by networks of drains to prevent water from ponding on the soil during the winter. Or ditches may drain wetlands, making the land suitable for pasture or crops.

Flood control schemes are designed to protect people, property and infrastructure. Stopbanks and flood gates hold back streams and rivers when water flows are high, rather than allowing water to naturally enter the adjacent floodplains. These measures protect us and our land use, but they can dramatically change the landscape.

For example, only 1% of the original wetlands remain in the Hamilton Basin. Wetland loss has meant severe habitat reduction for fish such as eels. When we drain wetlands, we lose more than habitat. We lose the systems’ natural sponges and filters, as wetlands retain rainwater and reduce flooding downstream, and remove soil and nutrients from run-off.

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Acknowledgement: The University of Waikato Te Whare Wānanga o Waikato

Balancing the issues

Responsibility for the issues presented in this interactive does not rest with individual groups or businesses. We all benefit from flood protection, sealed roads and food that comes from the land.

Environmental education is about exploring issues from many points of view and recognising the importance of learning to live in balance with the environment.

Water quality is a top concern for most New Zealanders. There are actions that we can all take to conserve water and reduce our impacts on our freshwater systems.

Select here to view the video transcript and copyright information.

Acknowledgement: The University of Waikato Te Whare Wānanga o Waikato and Waikato Regional Council