Water is a Living Archive: Examining myths of where various urban streams come from: Pt. 1: Kellogg Creek
July 2, 2014 § 3 Comments
Have you ever heard rumors that water in various urban streams in Los Angeles originates in significant part from irrigation runoff?
It’s true that car wash and irrigation runoff are often seen flowing into storm drains. Dry season (summer) is the time these activities are most likely to take place. In the case of the Los Angeles River, a good deal of the river’s dry season flow comes from point source discharges rather than groundwater: one report says this figure is about 80% (Arup, 2011). Point sources include storm drains which convey irrigation runoff and carwash runoff, but also effluent from wastewater treatment plants. Flow data collected in 2000-2001 by Stein and Ackerman (2007) indicated that on the average, half of dry season flow in the Los Angeles River originated as effluent from wastewater treatment plants and half from storm drains.
As Josh Link puts it, the Los Angeles River, the end of pipe destination for a good deal of imported tap water, is effectively a confluence of numerous watersheds: The Sacramento and San Joaquin River watersheds, the Colorado River watershed, and the Los Angeles River watershed. Water from three great watersheds is dammed, and then transported via hundreds of miles of aqueduct and other conveyance systems, over fields, deserts and mountain ranges, combined with pumped local groundwater, consumed by Los Angeles, then collected and treated to become effluent contributing to a river whose concrete channel has isolated it from its original hydrologic context where it would have been fed throughout the year by precipitation collected and released slowly from storage in the ground. In this way, the Los Angeles River epitomizes rivers of this current epoch, in which the human impact on our landscapes rivals that of other environmental and geological processes.
But it’s also often overlooked that in addition to stormwater and irrigation runoff, some storm drains actually convey perennial tributaries of rivers. Some of these tributaries have a substantial amount of flow. In northeast Los Angeles, the North Branch of the Arroyo Seco has a name as well as a documented history. In Pomona, the stream my geology teacher refers to as ‘Snow Creek’ (for the fact that it runs through Snow Creek Park) is a perennial creek that managed never to get an official name. One of the smaller flows on the campus of Cal Poly Pomona has been informally named ‘Kellogg Creek’ by the university community. It runs for only a very short distance before it disappears into a drain. Despite the efforts of developers to have drained any ground worth building on, we simply have not been able to stop the flow of these creeks.
Yet, in each of these instances, the origin of these creeks has been subject to speculation. Where exactly do these waters come from? It seems easier to believe that irrigation runoff would be a major component of these streams than actual groundwater. Could there be anything natural about a stream like Snow Creek, which appears to originate from a pipe, and eventually is rerouted back into a pipe?
PT 1: Kellogg Creek
Kellogg Creek is the informal name of a small creek on the campus of Cal Poly Pomona. Its waters eventually flow toward San Jose Creek and the San Gabriel River. Kellogg Creek issues forth from Box Canyon, in the San Jose Hills on the northwest border of Cal Poly Pomona. Box Canyon is now part of the Voorhis Ecological Reserve. Aside from the encroachment of a cemetery at the head of the canyon, the watershed is largely undeveloped, and vegetated with Southern California black walnut and coastal sage scrub. Currently, after two extremely dry years, this stream is barely showing anything that could be called above-ground flow.
Botanist Curtis Clark suspects irrigation runoff from the cemetery’s well-watered lawn contributes to Kellogg Creek’s flow, since a portion of this lawn is situated inside the catchment. Indeed, the ability of irrigation runoff to raise groundwater levels has been documented in the Antelope Valley, where runoff from agricultural irrigation may be responsible for a 45 foot rise in groundwater levels (Leighton, 2003) that has occurred under parts of the valley that are primarily devoted to agricultural use (other parts of the valley have experienced subsidence due to overpumping). But is the amount of irrigation used by Forest Lawn enough for it to be a significant source of water for Kellogg Creek? Jeff Marshall, geomorphologist, offers another possible origin for the water of Kellogg Creek’s water. He points out that Kellogg Creek is in line with a series of surface water features on campus that coincide with the San Jose fault. The friction caused by a fault sometimes causes a layer of clay-sized particles to form. This clay layer can become a barrier to underground water movement, and can cause groundwater to rise to the surface in spots.
Recently, I had a chance to test samples of water from these three urban creeks with the help of Debbie Kunath (GIT) in the lab of Dr. Stephen Osborn at Cal Poly Pomona. I hoped that testing could clarify how much of the surface flow of these creeks originated from irrigation (tap water), or ground water.
“Water is a living archive,” Dr. Stephen Osborn told me. It retains elements from where it originated, and picks up others from places it passes through, including traces of human use.
Measuring the amount of fluoride or chloride present can help us figure out how much of a given sample of water originates as tap water. Fluoride can be naturally present in groundwater. However, it is commonly added to municipal water to promote dental health. Chloride levels in water can be affected by use of inorganic fertilizers, landfill leachates, de-icing salts, or sea water intrusion. But it can also be related to the use of chlorine in water purification processes (WHO, 1996). Nitrates in water can also be naturally occurring. High levels might be a clue as to whether the water was once used to irrigate fertilized landscapes. Levels of > 1 ppm are considered a sign of human influence (such as use of inorganic fertilizers and presence of animal manure). Levels of > 3 ppm may indicate contamination (EPA, n. d.).
Kunath used ion chromatography to test water I collected from Kellogg Creek on 5/18/2014, north of Building 1, at the mouth of Box Canyon. The results for Kellogg Creek were:
- Fluoride = .206 ppm
- Chloride = 2.19 ppm
- Nitrate = .490 ppm
These numbers can be compared to levels of fluoride, chloride, and nitrates in municipal (tap) water distributed by the City of Pomona and Cal Poly Pomona. Both the City of Pomona and Cal Poly Pomona mix groundwater with imported water from both the Colorado River and the State Water Project to distribute as tap water. Municipal water at Weymouth Water Treatment Plant, La Verne (imported by MWD via the Colorado River Aqueduct):
- Fluoride = 0.7-1.0 (range)/ 0.8 (average) ppm
- Chloride = 84-94 (range)/ 93 (average) ppm
- Nitrate = Non-detect-1.8 (range)/ Non-detect (average) ppm
Groundwater used by the City of Pomona:
- Fluoride = .19-.66 (range)/ .29 (average) ppm
- Chloride = 9.9-130 (range)/ 80 (average) ppm
- Nitrate = 2.1-31 (range)/ 17 (average) ppm
Groundwater from a well on the campus of Cal Poly Pomona:
- Fluoride = .2-.3 (range)/ .2 (average) ppm
- Chloride = 81 (range)/ 81 (average) ppm
- Nitrate = 52-59 (range)/ 55 (average) ppm (must be blended with imported water to be potable)
These numbers show that levels of fluoride in Kellogg Creek are very low compared to imported Colorado River water, and within the range of naturally occurring fluoride in local groundwater. Levels of chloride in Kellogg Creek are much lower than both imported Colorado River water and local groundwater. Levels of nitrate in Kellogg Creek are within the range of imported Colorado River water, but much lower than local groundwater. Although the results from testing these three variables would seem to suggest Kellogg Creek might be good quality groundwater, more variables need to be tested to come to a solid conclusion. Other questions that remain: Would different results be obtained if Kellogg Creek water is tested after the very end of the dry season, after irrigation at the cemetery has most likely to been at its peak? Though we tested at the end of ‘rainy’ season, this is also the third year of a drought that started in 2012 (Farber, 2014). Moreover, do the results indicate whether water of Kellogg Creek originates from the catchment itself, or from underground water from elsewhere, forced upward by barriers to its underground flow? STAY TUNED: Ion chromatography results for the North Branch of the Arroyo Seco and Snow Creek, two watersheds which are almost entirely developed, will be described in a future post.
Arup. (2011). Hydrology and Water Quality, from Cornfield Arroyo Seco Specific Plan and Redevelopment Plan Draft Environmental Impact Report.
California State Polytechnic University, Pomona. (2014). 2013 Water Quality Report.
City of Pomona. (2011). 2011 Annual Water Quality Report. Public Works Department, Water/Wastewater Operations.
EPA. (n. d.). Estimated Nitrate Concentrations in Groundwater Used for Drinking. www2.epa.gov/nutrient-policy-data/estimated-nitrate-concentrations-groundwater-used-drinking#main-content.
Leighton, D. A. and Phillips, S. P. (2003). Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California. U. S. Geological Survey Water-Resources Investigations Report 03-4016.
Stein, E. D. and Ackerman, D. (2007). Dry Weather Water Quality Loadings in Arid, Urban Watersheds of the Los Angeles Basin, California, USA. Journal of the American Water Resources Association (JAWRA) 43(2): 398-413.
World Health Organization. (1996). Chloride in Drinking Water, in Guidelines for drinking-water quality, 2nd ed. Vol. 2. Health criteria and other supporting information. Geneva.