9 Effects of Changing Water Use
River and water-based activities in the Waitaki Catchment are affected by water levels. Within the discussion tables of this report, there is comment on the effect of water levels on each activity discussed.
This is a very challenging factor to assess for water-based recreation activities because while one water flow level will be positive for one activity or form of activity it will be negative for others. Balancing up the positives and negatives becomes a difficult subjective exercise. It is not considered that the information in this report leads to a confident assessment of acceptable water levels for individual water bodies.
The difficulty of conducting primary research to find an appropriate flow level for the Waitaki River was experienced by the Project Aqua Boffa Miskell, Robb Greenaway 2003 study.
In this study respondents were asked a series of questions about river conditions, including:
- whether and how they checked flow levels prior to their visit
- effects of high and low flows
- knowledge of a minimum, preferred or maximum river flow.
Respondents were also asked if they had ever visited the Waitaki River and been dissatisfied with the conditions. "Forty-five percent of river survey respondents recorded yes, as did 46% of 'qualified' community survey respondents" (Boffa Miskell, Rob Greenaway & Associates, 2003b, p. 22).
This response seems quite low as the Waitaki River has fluctuating conditions that on some days are likely to dissatisfy participants. The survey was predominantly from respondents who were using the river during high flow conditions and so may be biased towards those who are satisfied with high flow conditions. The reasons given for visitor dissatisfaction were in order of selection for the recreation survey were: flooding (35%), other (26%), fluctuating levels (13%), low flows (13%), dirty water (7%), not enough fish (3%), problems with access (2%), dirty farm pollution (1%), overgrowth of scrub - gorse, broom etc (0%) (Boffa Miskell, Rob Greenaway & Associates 2003b, p. 23). Results from the community survey were similar.
While respondents were asked if they were ever dissatisfied on a particular day this does not mean that they would never want particular conditions to occur. A comparison can be drawn between someone visiting a ski field where they cannot get onto the mountain for a day due to snow falling. This does not mean that the skier doesn't like snow fall, as snow is obviously essential for skiing. It is a similar case for some things that dissatisfy river users, such as flooding or fluctuating river flows. While on one day these conditions may be dissatisfying, overall they enhance a particular activity. Questions that may have identified these factors were not asked in the recreation study and so which factors that are dissatisfying one day but complimentary overall cannot be stated from these survey results.
Respondents were asked if they checked the river conditions before their visit. "A total of 31% of respondents checked the river flow before visiting the Waitaki" (Boffa Miskell, Rob Greenaway & Associates 2003b, p. 23). This result cannot be considered as representative of the proportion of total users who check the river before visiting as those who checked the river and chose not to visit the river because of conditions during the survey period would by definition not be part of the survey sample. Because the river conditions were high during the survey period it can be assumed that there was a significant number who checked river flow conditions and chose not to visit. So the number of respondents who check the river before visiting within the total river user population is likely to be higher than the figure stated from the survey results.
The information sources used by respondents to check the river are also likely to be biased. The results for sources of information for river use were stated as: visually (48%), word of mouth (20%), newspaper (14%), telephone (0800, 0900) (14%), internet (5%). It cannot be known how many respondents checked the river by whatever means and chose not to visit because of what they found out. So the means that they used, for example internet and telephone, will be underrepresented because they did not venture to the river and have the chance of being surveyed. It should also be noted that those who are out of town do not have the chance to visually check without first travelling a significant distance to the river so are likely to check by some other source, such as telephone or internet.
As has been stated earlier in this report, it is believed that the high river flows during the survey period influenced who participated in the survey. As the river was flowing at a consistently high rate survey respondents were those who were prepared to participate in recreation activities during high river flow conditions. Respondents were asked if they could state their minimum, maximum or desired flow level in cumecs for their preferred activity (Boffa Miskell, Rob Greenaway & Associates 2003b, p. 24). "37% of respondents said they knew a minimum, maximum or desired flow level in cumecs (cubic metres per second) for their activity" (Boffa Miskell, Rob Greenaway & Associates 2003b, p. 24). Basic statistical analysis was completed for the data which gave calculated: minimum mean flow 241 cumecs; preferred mean flow 313 cumecs; and maximum flow 425 cumecs (Boffa Miskell, Rob Greenaway & Associates 2003b, p. 25). Mode and median flow were all within 25 cumecs of the mean for the three reported measures except for the mode preferred flow which was 350 cumecs.
Although desired and preferred are similar words, both were used interchangeably in the survey (Boffa Miskell, Rob Greenaway & Associates, 2003b, p. 43). It is not known how these words may have been interpreted differently by respondents and what effect this had on results.
For each fishing activity - trout fishing (n=37); trout/salmon fishing (n=35), salmon fishing (n=38) and whitebaiting (n=10), All (n=120) - a chart represented the preferred flow. Again these results should be considered with caution because of the flow level during the survey period, the time of the survey and also the small sample size of each group that was surveyed. The results showed that there was little difference between the groups and the most common combined mean for 'All' was between 301-350 cumecs. This can be interpreted as the preference for any one day on the river but does not mean that there is not a preference for the river at some times to flow higher or lower than that preferred flow rate. Significantly, respondents were asked for one preferred flow rate not a preferred range which may be more appropriate for some activities which are enhanced by changing river levels such as fishing and jet boating.
Respondents who could not state a preferred flow in cumecs were asked if they would prefer a flow that was: a lot lower than today; a little higher than today; like today; a little higher than today; or, a lot higher than today. These results confirm that the survey flow range was high. While a high proportion preferred how the river was on the survey day this was less when respondents were surveyed in higher flow conditions. A very small proportion wanted the river a little higher and no one wanted the river a lot higher (Boffa Miskell, Rob Greenaway & Associates, 2003b, p. 26). The results show that more people wanted a lower river (95) than the day they were surveyed on than those who preferred the day they were surveyed on (92). This is significant considering respondents had freely chosen to participate and does not include those who were not participating because they considered the river too high.
"Respondents were asked how often their main activity was not possible or seriously limited due to high or low flows on the Waitaki River" (Boffa Miskell, Rob Greenaway & Associates, 2003b, p. 27). Without defining what is a high or low flow it is difficult to interpret these results. Environment Canterbury mean cumec readings since 1999 to the end of the main survey period (four years) show that the river flowed lower than 278.8 cumecs 20 percent of the time and flowed higher than 450.6 cumecs 20 percent of the time. [Information extracted from mean hourly flows (cubic metres per second) for the Waitaki River at Kurow (site 71104) supplied by Environment Canterbury for the period. Environment Canterbury consider the information provided as audited information.] Below and above this range gives an arbitrary low and high flow range. But without asking respondents what they consider a high or low flow level it is not possible to know what respondents meant when answering this question.
A low flow trial was completed to gather information and data that would assist in the determination of a residual flow regime, should Project Aqua proceed. The trial was achieved by progressively dropping the river from its typical mean flow of about 350 cumecs down to 150, 120 and 90 cumecs. Each flow was maintained for 24 hours to be observed by interested stakeholders (Boffa Miskell, Rob Greenaway & Associates, 2003a, p. 29).
The results for this trial need to be treated with caution because of the low sample sizes and short time of the study. For example 12 people assessed the river at 150 cumecs. Of these 12 the results were: perfect (1); very good (1); adequate (in places) (1); disappointing (2); completely unsatisfactory (7). In total there were 61 assessments of the river at four flow levels and the maximum number of assessments of one flow was 22 respondents (120 cumecs).
This trial asked about the flow of the river at each level for a 24-hour period. The effects of running the river at that level for a prolonged period of time on recreation experiences are not known. It is considered by a number of observers though that the river flow is likely to drop further the longer it is run at a low flow level and a trial needs to be run for longer than 24 hours to get a true indication of likely river conditions.
There is a large gap between 150 cumecs (the highest lowered level) and 350 cumecs which is a typical flow. Recreationists' opinions between these two flow levels are not known.
Respondents were also asked the following questions
If Project Aqua resulted in similar flows to those you experience today in the lower Waitaki River, do you think that this would adversely affect your future enjoyment of the river for your recreation activity(ies)?
The following summary of views were: not at all (6); a small amount (3); it will be different at first but I will get used to it (4); the quality of the experience will be changed for the worse (31); I probably would not pursue this activity here any more (7) (Boffa Miskell, Rob Greenaway & Associates, 2003a, p. 31).
The challenges faced in the study discussed above illustrate the complex issues involved when considering acceptable water flow levels in the Waitaki Catchment for recreation activities.
