Understanding Waimakariri River Flows & Weather Forecasts
If you're new to kayaking on the Waimakariri River, here's is some guidance around what to check, and what different weather and flow conditions will be like in relation to multisport.
- River Flows: Waimakairi Esk Flow Gauge: Below 0.7m and dropping. Waimakariri Otarama Flow Gauge: Below 130 m3/s and dropping.
- Wind Speed: Canterbury High Country Wind @ 1000m: Below 50 km/h.
- Rain & Weather: Arthur's Pass, Carrington, & Esk Rain Gauges: No rain in last 24 hours. Arthur's Pass Forecast: Good weather, warm and dry. Freezing level above 1000m.
1. Check the River Flow Levels
There are four electronic gauges on the Waimakariri River, all maintained and monitored by Environment Canterbury. For paddling the Coast to Coast route (Mt White to Gorge Bridge) we are interested in the two uppermost sites; Esk & Otarama.
The Esk River is a smaller tributary that flows into the Waimak' just above the start of the gorge (about 25km downstream of Mt White). The Esk Gauge is located in the Waimakariri River, about 2km downstream of the Esk/Waimak' Confluence. This gauge will normally provide the earliest confirmation that our river is rising (or falling).
The Esk Gauge gives a reading in metres (how deep it is at that spot). A good paddling range for this gauge is between 0.25m - 0.7m. Make sure the trend is clearly dropping, (or steady at very low flow).
The Otarama Gauge is located on the Waimakariri River around 5km upstream of Woodstock, (or 20km upstream of Gorge Bridge).
Because this gauge is measured in cubic metres per second ("cumecs"), it is often the reading we use when communicating the flow level between paddlers, and is the preferred gauge used by our guides.
However, because of the technical nature of calibrating this type of gauge, the reading can often be pulled out of accuracy by a shift in the loose gravel river-bed. The riverbed is most likely to change shape during times when the river is changing flow-rates quickly. So be aware that this gauge may not always be true and accurate, especially following a major flood, or when manual calibration hasn't been performed in a while. Obtaining local knowledge of the gauge's current accuracy is the key, particularly when 20 or 30 cumecs variation would mean the difference between going paddling or not.
A good paddling range for the Otarama gauge is between 30 - 130 cubic metres per second.
What it's like at Low Flows
At flows around 30 cumecs, the top section of the river is a scrape and it can be challenging to stay in the correct braid. The Rock Gardens will definitely have rocks protruding the surface with a thread-the-needle line in spots. Bluff corners will be tight with large boils, and wave trains like Salmon Rapid will be rough and bouncy. You will obviously have a slower trip downstream with less speed in the river. Many novices actually prefer a low flow, as it feels like you have more time to move your boat into position, and while the features can be more technical, they can seem less intimidating in a way.
What it's like at Medium Flows
I think the Waimakariri River is at it's best around the 80 cumec level. The top braids can still provide a challenge in navigation, but when done right your efforts are rewarded with smooth flowing lines from one branch to the next. The Rock Gardens are usually the most challenging at this flow. The rocks are still protruding and need respect, but there is also a decent amount of water kicking up quality wave trains to make things extra interesting. Bluff corners will have a little more room, and some will have multiple line options (such as going inside or outside of the boils). For the adequately skilled, wave trains are their most fun (but not overly difficult) at this flow.
What it's like at High Flows
At levels around 120 cumecs, you better be sure the river is actually at that level, and not higher due to gauge miss-calibration mentioned earlier. I love guiding at this flow. To be completely honest, maybe that's partly due to the noticeably less physical effort required to make the distance. But, I also know that if we can get clients on a good line early, we can avoid a lot of the bigger more powerful features that exist at these levels. On guided trips, we tend to actually have less client-swims, which seems counterintuitive I know. Of course, un-guided at these flows will feel like you have way less time to determine your line. Plus, any mistakes can quickly get out of control due to the speed and width of the river. Self-rescuing becomes much harder, and any swims become longer and colder. We find ourselves rescuing un-guided parties most often during higher flow days.
2. Check the Wind (Very Important)
Of all the factors that force us to call a guided trip off, a strong westerly wind would easily be the most common. While it seems obvious to check the river level before going kayaking, checking wind-speed is often over looked, or underappreciated. Knowing which forecasts to check, and what they mean for kayaking down the Waimak' is a constantly evolving art-form of trail and error. I've made the call to go on well over a hundred trips now, and here's what I'd like to tell you about wind...
Metservice is New Zealand official forecaster, and while they can be a bit vague at times compared to other computer modelled websites such as metvu, or windy, I like to know that there is a real person (who is certainly more qualified than me) looking at the data and providing a plain language interpretation. If the forecast is vague sounding, I take that into account and prepare for a range of possibilities. Remember a forecast is a "forecast", not a prediction.
A good wind speed for paddling on the Waimakariri River is anything up to 50 km/h. However light northwesterly is ideal. Interestingly, light or no-wind in the forecast can actually produce a strong head-wind in the Gorge during summer. A tailwind is nice, to a point. Once foretasted wind speeds from the western half reach gale 65 km/h or higher, you can easily get blown off your line in your long lightweight boat (and into trouble). I've seen plenty of good paddlers blown upside-down at wind forecasts around 65 km/h.
3. Check for Incoming Rain & Weather
If things are looking good so far, you better be sure they're going to stay that way. More rain in the catchment could mean the river is on the rise, or worse, about to flood. A cold southerly change could be just around the corner, bringing hail and dangerously cold temperatures (even in February) while you're isolated in the Gorge.
Rainfall at Arthur's Pass, Carrington, & Esk
Pretty much all the rain that may be falling (or has recently fallen) around these gauge sites is going to make it's way into the Waimakariri River. So it's super important you check them. Anything more than about 10 mm (total per rain event) is going to increase the river flow. More than about 30 mm total is when we start to think about whether the river could spike outside of recommended flow ranges. Of course, it all depends how high the river was to begin with, the duration of rain, how saturated the ground is, the effect of evaporation... basically it's bloody hard to say how much rain is equal to how many cumecs the river will gain. If you can figure it out, please let me know! I have a pretty good feel for it now, but essentially you want no rain in the last 24 hours to be safe.
Looking at the forecast in the Arthur's Pass area will give you an idea of any rainfall amounts that are expected. There are three sites you can look at; Carrington Hut, Carroll Hut, and Avalanche Peak. All three are relevant.
It's also worth looking at the freezing level (lower is colder). A freezing level of around 3000m or higher would be ideal, but things are more than tolerable down to 2000m with the right layers on. If you're seeing freezing levels below 1000m mid-summer it's likely to feel icy-cold, especially once you're damp and have a wind-chill factor involved.
Consider a Guided Trip
Remove the guesswork, and have a safer experience on one of our Waimakariri Gorge Trips. Not only can we accurately assess the conditions, we'll also provide a complete safety system including rescue and communication options. Plus, we think you'll learn a lot from our guides who know this river better than most. More info here.