this is a draft and I am still writing it
Water Temperature Monitoring Program in Kookipi Creek – Progress Report 2002
I. Introduction
At the request of the Ministry of Forests (MoF), Small Business Forest Enterprise Program, the Ministry of Water, Land and Air protection (WLAP) installed thermistors in the west fork of Kookipi Creek during the summers of 2001 and 2002. The valley of the west fork of Kookipi Creek (West Kookipi) is scheduled for removal of much valley bottom timber (aside from riparian buffer strips) along a 6 km length under a “large take-large leave” plan. There are no known resident populations of resident fish in West Kookipi; however, resident bull trout are found in the main stem of Kookipi Creek, and West Kookipi provides important temperature regulation, providing a source of significantly colder water. For this reason, maintaining low summer stream temperatures in West Kookipi is desired.
I. Physiographic Setting
Kookipi Creek is part of the Nahatlatch watershed and drains into it just below the Nahatlatch Lakes. Drainage basin size for Kookipi Cr. is ~160 km² and for West Kookipi, ~33 km² (SilvaWest, 1997). See Figure 1.
West Kookipi has headwaters at an elevation of ~1500 m.a.s.l., and flows in a northerly direction for its upper 8 km of length, gradually curving to flow northeast, in a U-shaped valley. Below ~1160m.a.s.l elevation, its course becomes more strongly oriented to the east, and the valley undergoes a transition to V-shaped cross section, steepening in gradient, for its last 2.5 km. West Kookipi enters Kookipi main at 800m.a.s.l. It is this steep lower section of West Kookipi that blocks fish passage upstream.
West Kookipi is underlain by well–jointed granitic bedrock of the Scuzzy Pluton. The U-shaped portion of the valley bottom has till deposits overlain with fluvial sediment; the lower V-shaped section has colluvial surficial materials.
III History
West Kookipi was unlogged until 1999, when two blocks were harvested. Thermistors were placed in June 2001, and removed in September 2001. Thermistors were placed again in June 2002. Two more blocks were logged in 2002;the first was being harvested when sensors were placed in June 2002; harvest was ongoing in the second of these blocks when the thermistors were removed in October 2002.
Block Harvest Date Area (ha) Channel Parallel Distance*
A48742 Block A (opening 19) 1999 27.6 0.9 km RB
A51484 Block A (opening 29) 1999 35.4 0.75 km LB
0.6 km RB
A53968 Block A June 2002 30.9 0.75 km LB
0.75 km RB
A53973 Block A October 2002 88.1 1.5 km LB
1.5 km RB
*Channel parallel distance is defined as the length of the perimeter of the RMA bounding the cutblock. Total length of channel between the two stations is 6 km, so total CPD is 12 km (~ 6km on each bank).
Note that, due to the timing of harvesting dates, the net difference in harvested area between the 2001 and 2002 surveys is only 30.9 ha (block A53968). However, the harvested CPD increase is 1.5 km, or 12.5% of total stream length between thermistors. (1.5/12)
Kookipi West is classified as an S5, valley bottom stream. A 30 meter, riparian management area (RMA) has been prescribed along the length of the stream in order to protect wildlife habitat values and bank and channel stability (as per MoF/MELP 1998 agreement on valley bottom streams in Chilliwack Forest District).
IV Results
It was expected that the observed temperature pattern in Kookipi West would be similar to that seen in temperature sensitive streams elsewhere, namely warming downstream. In fact, the observed pattern was one of cooling downstream, during periods of warm temperature. By contrast, during periods of cool weather, and at night, the stream tends to warm downstream, but temperature difference is only minimal, compared to the magnitude of daytime variation. See Figure.
A climate station was not installed in Kookipi drainage. The nearest Environment Canada
Stations are at Hells Gate and Lytton, respectively. For the purposes of this study, periods of cloudy weather and rainfall over the south Coast during the summer months were noted by observation; they correlated strongly with the observed fluctuation in temperature described below.
Generally speaking, during warm, sunny weather, the upper station is the same temperature as the lower station, or slightly cooler, at night. It warms more rapidly than does the lower station, and peaks at 2.5-3C warmer, during early afternoon. It then cools more quickly in the evening, and is the same, or slightly cooler than again at night.
During periods of cloudy, wet weather, diurnal temperature variation still occurs, but the magnitude is much reduced, and the upper station is similar in temperature to, or slightly colder than, the lower station. Maximum temperatures during cloudy, wet weather, are often lower than the minimum temperatures during hot sunny weather immediately preceding them.
In order to discuss any effects of harvesting on stream temperature it is first desirable to understand what causes the observed diurnal variation. Based on the orientation and aspect of the valley, and valley morphology (V and U shaped), the headwaters section of the channel (including the upper station) has a north-south orientation and tree cover is discontinuous. Sky exposure for the channel is high, and channel gradient is low. At the site of the lower station, valley orientation is east-west. The channel is narrower, and sky exposure is much less for both this reason (trees overhang channel and shade it) and due to the north-aspected slope on the south valley wall. Channel gradient is relatively steep.
Overall, then, the lower station is more shaded by trees and valley walls, less exposed to the sky (overall – note that it is technically possible to be shaded but still have a high exposure to the sky), and steeper gradient.
Combining these factors results in the conclusion that the stream, at the upper station, is affected primarily by direct solar heating. The N-S trending valley with open walls receives morning sun early in the day, and during the warmest part of the day sunlight falls directly on the stream. Gradient is low, so groundwater contribution does not increase significantly downstream, reducing the effect of groundwater moderation on stream temperature. At night, the sky exposure is high, so the stream loses heat quickly by radiation, cooling rapidly.
At the lower station, the opposite occurs. The channel is at the toe of a north-aspected slope, and is shaded by the trees on either side of the narrow channel, so direct solar input is minimal. Stream gradient is high, so the groundwater contribution is significant; cold groundwater exerts a significant moderating effect on temperature fluctuations. At night, the sky exposure is low, so heat loss by radiation is minimal, resulting in slower cooling than at the upper station.
Countering these effects somewhat is the effect of station elevations. The upper station is located at ~1310 m.a.s.l; the lower station is at 970 m.a.s.l. Based on adiabatic lapse rate, this will result in an estimated air temperature difference of approximately 2 degrees between upper (colder) and lower (warmer) stations, which would tend to moderate somewhat the effects of aspect and groundwater contribution. However, during the period of interest (summer and early fall), air conditions are unlikely to be stable, hence strict adiabatic lapse is unlikely.
If, as discussed above, diurnal temperature variation is mostly a function of aspect and gradient, and maximum temperature is determined mostly by weather conditions (sunny days, warmer water); then a direct comparison between 2001 and 2002 observed temperatures must take these effects into account. Comparing mean downstream temperature in 2002, to mean downstream temperature in 2001, would show that mean downstream temperature was warmer in 2002; however, this is directly attributable to the fact that summer and fall 2002 was sunnier and warmer than summer and fall 2001.
However, we can use upstream temperature, which is only affected by weather fluctuations, as a control against which to establish if the downstream variation in observed temperature is influenced by the harvesting carried out, or not. See Figure below:
In 2002, the mean observed downstream temperature for a given upstream temperature (as shown by the trend line) was slightly colder (~0.2 °C) than for the same upstream temperature in 2001. However, this difference is within the margin of error of the data, leading us to conclude that the difference between the two sets of observations is not statistically significant.
Examining only the warmest downstream temperatures, those of concern to fish, shows the same general pattern. Bull trout prefer water between 10-12 °C for juvenile growth, and 7-9 °C for spawning. Above 15 °C, bull trout are adversely affected, and are rarely found in waters routinely reaching this temperature. Observed temperatures in Kookipi Creek reached 15 °C only at the upstream station (once in 2001 and never in 2002). A downstream temperature of 9 °C was chosen as representing the warmest conditions (see Figure)
Again the results show no significant difference between 2001 and 2002; in fact uncertainty in the comparison is much higher (as indicated by lower r-square values for regression line).
