The SWPROD program calculates daytime net productivity, night respiration, and total community metabolism from a diel series of dissolved oxygen, temperature, and salinity measurements. An Odum approach is used for the solution of the oxygen-balance equation at a single station in a stream or as a difference between upstream and downstream stations. Net oxygen production and subsequent ... community metabolism of horizontal lake segments are calculated assuming a one-dimensional model using a finite-difference equation. The results are useful for general aquatic ecosystem characterization and as input to water-quality models for dissolved-oxygen analysis of aquatic environments. SWPROD is a revision of the USGS program J330.
Procedures for defining the diel oxygen relationship utilize dissolved-oxygen measurements to solve the basic oxygen equation. The applicability and accuracy of the procedures are limited by the assumptions. Reaeration is assumed to be constant over the 24-hour period. Advective transport must be absent or the quantity of oxygen so transported must be known. No assumptions concerning daytime respiration are made; therefore, values for gross production are not calculated. Any accrual or loss of water must be known. Turbulence must be low enough to permit observation of nighttime decline in dissolved oxygen. There must be sufficient plant biomass present to provide a daytime increase in oxygen due to photosynthesis.
[Summary provided by the USGS.]