Table I. Fluxes of water, nitrate, and ammonium and volume-weighted NO₃^- concentration in stream water during the hydrologic year beginning 1 October 1984.

a Estimates reported here for annual flux in each watershed reflect a 1 L/s minimum detection limit set by performance of the trapezoidal flumes calibrated for low flow. For comparison, computed NO₃^- flux at flow rates to a 0.02 L/s minimum was 26 eq/ha from watershed no. 803 and 240 eq/ha from no. 804. NH₄⁺ flux at all flow rates was 2.7 eq/ha from no. 803 and 5.1 eq/ha from no. 804.
b Discharge during debris-laden flows, estimated as flows at rates >40 L/s; no flows of this magnitude occurred on the unburned watersheds.
c Approximate standard errors for these annual water yield estimates, computed by a Monte Carlo simulation based on errors in the high- and low-flow calibration functions, duration of the 19 December debris flow, and peak-flow sediment concentration, were 5.4% of the point estimate for watershed no. 775 and 13% of the estimate for no. 776.
d Annual NO₃^- flux and concentration estimates shown here for watershed no. 773 were weighted by a ratio (2.6:1) of mean prefire concentrations between watersheds 773 and 776 as measured during peak and recessional flows of 1983. This provides an estimate of performance by watershed 776 during 1984 had it not burned. Concentrations in no. 773 were consistently higher than those from watersheds further east in West Fork San Dimas Canyon, possibly as a result of greater exposure to onshore winds and elevated deposition of air pollutants rising from the Los Angeles Basin. The watersheds in Bell Canyon did not substantially differ prior to treatment.