Current Freshwater State

At the 2020 SOE report, the Flaxbourne River had one of the poorest attribute states in the region. A number of these factors were and continue to be explained by the land use, climate, and geology in the catchment which are discussed below. At the 2023 SOE report, we see improvements in the Flaxbourne River such as the Nitrate attribute improving to an A grade however the APSM attribute declined to a D grade, below the national bottom line. The Waima/Ure River did not have any declines in attribute state, having only an improvement in Periphyton to an A band.

Regionally, all sites are within the A-Band for the Nitrate attribute. At the 2020 SOE report, the Flaxbourne River was measured within the B band. This was the first year of SOE reporting with any site measuring in the B band for this attribute. The cause was a single very high measurement in February 2019, likely a direct input of fertilizer as the water was clear and E. coli concentrations were low. It is noted that at the 2023 SOE report, both sites in this FMU were A grade for Nitrate. This was also the case for Ammonia, which was unchanged between the reports.

The Flaxbourne catchment has little native vegetation remaining and landcover is now dominated by sheep and beef pastures. The dry climate in the Flaxbourne River catchment means that although livestock is grazed at low intensity, the impact of stock access to the waterway is relatively high. Naturally lower flows in the river and lack of riparian planting in some areas also means that the ecological system is more susceptible to changes from the natural conditions. This assists with explaining the high E. Coli concentrations and low MCI and APSM scores in the Flaxbourne River. In comparison, the relatively less developed catchment area of the Waima/Ure River, which has a higher proportion of native land cover and less pastoral development, has superior A band MCI, APSM, and E. Coli scores which were unchanged between the two reports.

The Periphyton band relates to algae and bacteria growth on the riverbed, measured through the amount of Chlorophyll per square metre. Too much periphyton growth alters pH, removes food sources, and alters habitats. Therefore, high growth can severely impact the overall ecosystem.

Periphyton growth is exacerbated by the amount of sunlight, high DRP concentrations, and a dry climate. Periods of high flow - often induced by high rainfall - assist with moving washing rocks and attached algae downstream. This washing effect does not occur in low rainfall areas like the East Coast Complex. Additionally, the Flaxbourne river is wide and shallow, allowing sunlight across the riverbed which in turn assists with algae growth. These natural characteristics in this FMU help to explain the significantly higher periphyton measurements in the Flaxbourne River compared to other waterways in the region. The Flaxbourne River is the only monitoring site with Periphyton cover in the D-band.

Accordingly, the natural geology and climate of the Flaxbourne River means this waterway is more susceptible to high DRP concentrations than other waterways in the region. However, the Periphyton attribute scores have improved in both waterways between the 2020 and 2023 SOE reports.

The current NPSFM allows limits for clarity to be converted into turbidity limits using site-specific correlations. At the 2020 report, the majority of monitoring sites were either not established or did not have enough data to derive a trend. At the 2023 report, the ECC FMU sites had enough data to derive a trend which is shown in the outer circle on the chart above. All sites scored within the A band.

The 2020 SOE report reported several comments regarding the parameters used in the WQI calculation for the Flaxbourne and Waima Rivers, as well as impacts of natural geology and human induced land cover in the catchments.

One example of this is the natural presence of limestone causes naturally higher pH values in rivers and stream in the southern part of the region, such as in the ECC FMU. pH regionally is highest in the Waima River and was likely impacted at this time by the significant and recent Kaikōura earthquake. This earthquake was determined to have likely had an impact on other parameters, such as elevated turbidity due to resulting slips putting increased sediment into the waterway.

Nitrate, Ammoniacal nitrogen and Nitrite are soluble forms of nitrogen that are easily taken up by plants. They are collectively referred to as ‘Dissolved Inorganic Nitrogen’, abbreviated as DIN. High DIN concentrations can cause excessive growth of aquatic plants such as algae. This is not only visually unpleasing, but the algae smother available habitat for many aquatic insects, which in turn are a food source for fish. This can cause a significant reduction in biodiversity.

Naturally, DIN concentrations are low. The highest spikes in DIN concentrations at the 2020 SOE report were observed in two rivers, one of which was the Flaxbourne River. In both cases, the high DIN values were observed during dry weather condition, ruling out rainfall run-off as the source. The most likely cause was aerial fertilizer application over small tributaries or the main river.

The highest oxygen concentrations in the region were observed in two rivers, one of which is the Flaxbourne River. The bed of this waterway was often covered in thick stands of filamentous algae which relates to high oxygen, as this is needed for such algae to survive, as well as high DIN concentrations as discussed above.

Municipal supply

Ward domestic water is supplied through a privately owned, reticulated water scheme which draws water from a shallow well in the Flaxbourne River and supplies 70 properties in the township. This is a minor water Resource Consent regionally but a large singular take consent in this FMU.

The northern part of this FMU is also connected to the Black Birch water supply scheme. This is a limited area in the north and east of this FMU.