FLOOD10356

• County: Delta
• Title: North Fork Volunteer Water Quality Monitoring Project - April 2001-April 2002 Data Report
• Date: 9/30/2002
• Prepared For: North Fork River Improvement Association
• Prepared By: CSU Cooperative Extension and North Fork River Improvement Association
• Floodplain - Doc Type: Floodplain Report/Masterplan

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3.2 Nutrients

Nitrogen

Nitrogen concentrations in the North Fork watershed were measured by nitrate-nitrite,
ammonia, and total kjeldahl nitrogen analyses. There were no exceedances of the State's
nitrate standard of 10 mgIL. In fact, most of the samples had nitrate-nitrite
concentrations below the laboratory detection limits. These limits changed during the
period of the study. Initially, the detection limit was <0.05 mgIL, then the limit was
raised to <0.3 mgIL in August of2001.

The State's chronic ammonia standard is 0.02 mg/L for these segments; however, over
most of the study period the laboratory's minimum detection limits (based on lab
technology) were higher than the standard, ranging from <0.05 to <1 mg/L. 'The highest
ammonia concentration was 0.21 mgIL, recorded at NF-3 on July 11, 2001. Potential
sources of nitrogen pollution in rivers can include fertilizer and wastewater treatment
plants.

Total Suspended Solids and Total Phosphates

TSS concentrations varied from station to station. The largest increases in suspended
solids could be correlated to storm events and spring runoff, where sudden large amounts
of rainfall or snowmelt eroded soil into the rivers. The East Muddy Station (EM-I) for
example, reflects the high concentrations of sediment in this system during spring runoff
(490 mgIL on April 25, 2001), and also after a large storm event (570 mg/L on August 9,
2001). The highest suspended sediment loads during the whole year were recorded
during or shortly after stormwater runoff events at NF-2, below Somerset, on August 9,
2001 (940 mg/L); and at NF-4, Hotchkiss, on October 10,2001 (620 mg/L).

TSS loads can also be correlated with increases in total phosphate concentrations. The
chart below shows how total phosphate concentrations increase in conjunction with major
stormwater and snowmelt runoff events. This is likely a reflection of the inorganic
phosphate that is sorbed to soil particles and washes into the river during erosion events.

Total Dissolved Solids

TDS are comprised primarily of calcium, sodium, and magnesium salts. TDS
concentrations increase dramatically starting near Paonia. This is likely a reflection of
inputs from irrigation. Irrigation water leaches through saline soils and washes out the
water-soluble salts. These salts then end up in the river. The highest TDS value was
recorded at NF-4, Hotchkiss, with a concentration of 1,270 mgIL on September 12, 2001.
Although there is no state standard for TDS, based on CSU references, waters above
1,000 mg/L TDS "may have adverse affects on crops and require careful management
practices" (SIA No. 0.506, Irrigation Water Quality Criteria, CSU).

Sulfates

Sulfate concentrations rose dramatically starting in the Paonia area and continuing
downstream. Above Paonia, sulfate concentrations are generally low, often below
10 mg/L. However, after Paonia they started to rise. The highest sulfate concentration

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