So, How’s the Water?

   This was an often asked question over the past three years as many of you encountered myself and other nps folks collecting and processing water samples (we were the ones sitting at the little blue table in the shade) along the river. At the time, we could not provide a whole lot of information because samples had to be sent to an outside lab or incubated for bacteria. Plus, it is difficult to make significant conclusions about a tributary’s water quality from a single sample. Now that we have about three years of data collected, we finally can make some sense (not much, but a little) of it all.

   Before I go any further, I want to state upfront that water quality data is difficult to interpret with a lot of confidence because of the high variability of the medium you are sampling. Water quality changes continually as subtle shifts in discharge (or flow) and turbidity (cloudiness) change. Also, sampling itself can be difficult to do in an accurate manner as one pool or riffle could have differing concentrations than another in the same stream, especially when it comes to bacteria. Keep that in mind as you read this. We did our best to sample as accurately as possible; but its the nature of water, as a fluid medium, to be difficult to draw statistically valid conclusions. That’s why I went back to being a botanist.

   The reason we were out sampling was for a study titled An Intensive Reconnaissance Sampling of Grand Canyon Tributaries which was funded by the nps Water Resources division, the State of Arizona Dept. of Environmental Quality (deq) and Grand Canyon National Park. Since so much information was being collected on the mainstem Colorado for gces, I wanted to inventory the water quality characteristics of as many tributaries as possible.

   Other studies have been done in the past on Grand Canyon’s tributaries, mostly in conjunction with studies where the main focus was the Colorado River. If you’ve read any of those studies, such as those done in the late ’70s and early ’80s, you may not be surprised by the conclusions of this most recent effort. What stands out about this study is that instead of a one or two shot sample, tributaries were sampled on a seasonal basis over three years to determine if water quality characteristics varied by season or by change in discharge. The major “core” tributaries (Tapeats, Kanab, Havasu, Vasey’s, Bright Angel, Paria, Little Colorado (lcr), Nankoweap, Lava Chuar, Hermit, Crystal, Shinumo, Royal Arch, National and Spring Canyon) were sampled at least eight or nine separate times from the spring of 1992 through the fall of 1994. Other tributaries in the study were: Matkatamiba, Warm (Lava) Springs, Three Springs, Stone, Monument, Clear, Deer, Saddle and Kwagunt creeks and the infamous Pumpkin Springs.

   So, anyway, how is the water??? Well, here’s a bit of a summary of what we found. You’ll have to plod through the final report for the rest. That report is available through the Resources Management division at Grand Canyon. It was also sent to all commercial river companies. 

   Basically, Grand Canyon’s tributaries all have the same following characteristics: hardness, high alkalinities (or buffering capacity), pHs around 8.5 (except for some of the warmer springs where pH is around 7.5) and dissolved oxygen levels in the range of healthy streams.

   Chemically, the tributaries can be broken into two categories: those with high amounts of total dissolved solids and those with low amounts of total dissolved solids. Unlike total suspended solids which are what cause high turbidity during flood events, total dissolved solids (or tds) represent the total amount of dissolved chemicals, minerals and trace metals in waters. tds is not just limited to calcium, magnesium, sodium and chloride. A clear stream can still have high tds if it passes through the right rock layers or if other impacts like mine tailings or pesticide use are occurring. tds is important to mention here because a high value in a stream tells you that there is more of a possibility of health problems (such as the runs or stomach problems) with these streams. These levels may be entirely natural, but can still cause problems and cannot usually be filtered out because of the tiny nature of the elements involved.

   It’s probably not too surprising that the streams found with low tds included Vasey’s, Thunder River, Shinumo, Tapeats, Deer, Bright Angel, Saddle, Clear and Stone Creeks, all emerging from the Redwall or Muav limestones off the North Rim. What may be of interest, is that tds levels did not vary much by discharge or season in these streams even though the larger tributaries fluctuated widely due to spring runoff.

   Those streams with high tds emerged from the lower carbonate strata: lcr, National, Kanab, Matkatamiba, Crystal, Warm Springs, Havasu, Spring Canyon, Kwagunt, Royal Arch, Hermit, Three Springs and Nankoweap creeks (listed roughly in order of decreasing tds). Of course, the lcr and Havasu make sense: high sodium chloride. The two most interesting components found in most of these streams were arsenic and sulfate. Arsenic levels were especially high in Crystal Creek which exceeded state health standards three out of eight times (and came close the other times). Others that were high in arsenic included: lcr, Kanab, Warm Springs, Havasu, Hermit and Spring Canyon Creeks. Currently, the thought is that these levels are most likely natural. Other interesting components found in these tributaries included chromium, zinc, nickel and copper. Kanab Creek exhibited the highest levels of these, especially in flood stage. The lcr would probably have high levels as well, but we were never able to sample at flood stage during the study. Sulfate was found to be high in National, Kanab, Nankoweap, Kwagunt, Royal Arch and Spring Canyon Creeks. Although no health standards exist for sulfate, high concentrations can cause “the runs” in some folks. As with the low tds streams, fluctuations in concentrations did not appear to be related to flow levels or seasons.

   Radionuclide (radioactive element) levels were sampled at a selection of tributaries on a less frequent basis. Gross alpha/beta (a good first cut analysis) concentrations were determined for all of the tributaries already mentioned except for Matkatamiba, Warm Springs, Stone, Monument, Clear, Deer, Kwagunt and Saddle. Some radioisotope and total uranium data were collected for the lcr, Havasu, Kanab and Pumpkin Springs. The only tributaries where radionuclides were found to be above the natural range were Hermit, Paria and Lava Chuar. Kanab Creek had the highest concentrations (well above health standards) during flood stage. Keep in mind, that it can be difficult to obtain accurate measurements for radionuclides because of the analyses used, but this information can at least give an idea of where these components occur at higher concentrations on a regular basis.

   And, of course, there are real ’weird chemicals’ waters. You know them when you see them: the Paria River, Lava Chuar Creek and Pumpkin Springs. The Paria always seems to be turbid and can have high levels of arsenic, chromium, lead, cadium, nickel, beryllium and gross alpha/beta radionuclides. It’s even worse at higher flows when health standards were exceeded— for all the above— during the sampling period. The Paria drains such a large area that its hard to point a finger at the source of these constituents without intensive sampling further upstream. The source could be entirely natural, though, considering that it flows through the Chinle formation. Lava Chuar, which passes through precambrian and volcanic layers, also showed high concentrations of arsenic, chromium, lead, zinc, copper, nickel and sodium chloride. And then there’s Pumpkin Springs, probably the only truly dangerous water we have in Grand Canyon. Arsenic levels at Pumpkin Springs were 1100 milligrams/liter in one sample (the state health standard is 50 milligrams/liter). This is not healthy. Pumpkin was also found to have high levels of zinc, but not high levels of total uranium. You probably know that arsenic in large amounts is extremely toxic. This is the only water in Grand Canyon where nps advises no entry. It might be a good idea to take that advice to heart.

   Last, but not least, is the bacteria part of the study. This work was not designed to find the pathogen responsible for last summer’s illness. That will be studied intensively this summer by Coconino County. The bacteria portion of the study sampled for fecal coliform, which is the bacteria most correlated with human contamination, and fecal streptococcus (strep.), which is more correlated with wildlife contamination.

   Conclusions can be split into two separate categories: 1) tributaries that showed high bacteria during periods of high turbidity and/or discharge, and, 2) tributaries that showed high bacteria during periods of low turbidity and/or discharge.

   In the first category we find the lcr, Tapeats, Havasu, Kanab, Saddle, Deer, Kwagunt and Nankoweap Creeks. Of note, neither the lcr nor Havasu produced high concentrations of either Fecal coliform or strep. bacteria over the eight times they were sampled. Concentrations did increase during higher turbidity, but no results came close to health standard exceedances. Again, this would probably change under a major flood. Tapeats Creek was probably the cleanest of all tributaries with very little bacteria, except once during a fall flash flood when concentrations most likely exceeded health standards. One can assume the bacteria was harbored in streamside sediments from past upstream recreational use. Kanab and Saddle creeks exhibited this same pattern of high fecal coliform during turbid or flood events.

   The tributaries falling under category 2 were Bright Angel and Shinumo creeks. Both streams experienced high recreational use at the time of sampling but did not have high turbidity (possibly due to bigger flows and high velocity waters to flush out suspended sediments), yet exhibited high fecal coliform concentrations. When turbidity was high, though, fecal strep. tended to be higher meaning wildlife bacterial concentrations were being captured in surface run-off while no recreational use because of dangerous velocities (during spring run-off primarily) took place.

   In the case of Deer Creek, high clarity occurred moments before swimming or extensive wading. These activities quickly caused turbidity with sediments tending to settle approximately one hour after no use. During the high turbidity episodes, bacteria concentrations skyrocketed. A 24-hour sampling series was completed which showed this pattern of bacteria change. Concentrations dropped to almost zero as the water became clear again.

   Other tributaries did not exhibit such distinct patterns in turbidity or discharge. Royal Arch did not exhibit high fecal coliform concentrations, which one would think, but did have high fecal strep. levels. Crystal, Monument, Clear, Spring Canyon, Three Springs, Vasey’s, National, Stone and Hermit Creeks all followed somewhat of a pattern of high fecal strep. levels under most flows and turbidities. Matkatamiba fluctuated between high fecal coliform and high fecal strep. at different samplings with no change in discharge or turbidity. Warm Springs and Lava Chuar never exhibited any type of high bacteria concentrations (but remember that these streams had high tds).

   So, what can one conclude from this study? First of all, it is obvious that Grand Canyon’s water quality varies greatly when it comes to bacteria. But the real take home message is that most of the tributaries were found to have bacteria at sometimes high levels at least some of the time. This bacteria may not have been of human origin, but it does not have to be to cause illnesses. Animals can carry pathogens just as well as humans. My personal theory is that any stream exhibiting high fecal strep. characteristics (which was just about all of them at one time or another) may carry giardia as well. Unfortunately due to the sampling requirements necessary, I was not able to sample for giardia.

   Secondly, a good portion of Grand Canyon’s tributaries contain dissolved elements that, while most likely natural, can still be a problem to some folks who may drink them. These concentrations did not fluctuate as much as bacteria, but no matter how clear the water may be, the dissolved components are always present.

   The recommendation that I have made to the National Park Service is that all tributaries should be treated, filtration being the best method. Even tributaries running clear should be filtered because the simple act of filling a water bottle can stir-up the sediments that are obviously the culprit to holding bacteria. Care should be taken during heavy use/water play. Folks should be told to try not to ingest the water; they may want to consider any significant open wounds before entering. Having contracted giardia in the Canyon myself, I can attest that one does not want to experience it, if possible.

   I also recommended avoiding any water with high tds, since these constituents cannot be removed through filtration. If you really must collect water at Warm Springs, for instance, at least let folks know that the high dissolved solids may not sit well with them.

   Every person is going to react differently to waters like Warm Springs and that ingesting bacteria is pretty much a luck of the draw, so some level of awareness needs to be passed on to folks. 

   What I can say with confidence is that Grand Canyon National Park now has a current baseline of information on the majority of its tributaries which can be used as a basis for a long term monitoring program. Following trends in these tributaries for such a time period as a decade, for instance, will really allow us to understand the range of natural conditions in the tributaries and to pinpoint any unnatural inputs that may be occurring upstream. I have recommended such a program to the nps and can only hope that such a long term program will be instituted and the enormous amount of data collected for this study won’t be filed away to collect dust.

Linda Mazzu
 is now working as a botanist and
enjoying the rivers in southwestern Oregon