Can you define tailwater?
Agricultural tailwater is the portion of applied irrigation water or rainfall that is not infiltrated, evaporated, or retained by the plant, and instead flows off the field via surface drainage pathways and into conveyances like service ditches and canals.
First data slide findings where the STEC prevalence in the water column vs the sediment do not seem consistent with results seen elsewhere and general assumptions - can you comment more on this
In prior work in this region of California, we have found similar results of STEC in surface water and associated sediment. Multiple methods were used to test water, for example, 1 liter, 10 liters, and 100 liters were used as the test volume during the course of the study. These differing methods may have led to results being different from what others have observed with these sample matrices.
For the higher risk observed in riparian zones, do you think the driver is mainly surface processes, or subsurface hydrology and groundwater flow along the valley aquifer?
Our findings support surface-associated processes as contributors to elevated STEC detection near riparian areas, particularly winter flooding events that affected field soils. Wildlife movement and associated fecal deposition in or near fields may also have contributed.
This study was not designed to evaluate subsurface hydrology or groundwater flow within the valley aquifer, so we cannot assess their relative importance from these data.
In the section where you talked about ditches what was the source of the water in the ditches?
Run-off irrigation water or rainfall.
Is there correlation revealed between the positive river water sites and the distance to cattle farms at the region?
We are in the process of conducting a more thorough statistical analysis regarding proximity to rangeland and the occurrence of STEC in surface water.
Only 10 well samples? Why were so few ground water samples collected?
Nearly all produce farms enrolled in the study did not grant access for sampling of well water, resulting in the limited sample size of 10.
On the samples of water from the river how close were the sample from sewage treatment facilities?
Although most surface water sample locations were not close to a sewage treatment facility, a few sample sites were intentionally placed in proximity to these locations to test the association between STEC in surface water and proximity to a sewage treatment facility.
Walking down tributary creeks and streams during the dry season one sees many intact drub cow pies which clearly washed down during storms. Would blocking large mass transport reduce risk?
There are various management practices and structural changes to grazing land that can reduce the likelihood of dried cattle manure entering a surface waterway like a seasonal creek. For example, installing no-graze buffers sufficiently prior to and during the rainy season, or moving the cattle upslope prior to and during the rainy season, or, if possible, installing a retention or stock pond at the bottom of the field that will collect all surface flow during intense rainfall. Multiple publications are available for designs from such groups as NRCS, Cooperative Extension, etc.
Water samples from the river, how far from water treatment facilities where they are taken?
Water samples were taken at various points along the Salinas River at public access sites irrespective of proximity to WWTP; however, we did take samples at our Pajaro sites where two locations flanked (above and below) the WWTP near Watsonville, CA.