Tree leaf control on low flow water quality in a small Virginia stream

Abstract

Impaired water quality in a small stream was related to autumn leaf fall from riparian vegetation. Dissolved oxygen and pH decreased, and water color, specific conductance, iron, manganese, and bicarbonate values increased as the rate of leaf fall increased. Similar quality changes occurred in laboratory cultures of tree leaves in filtered stream water, but the five leaf species studied produced widely differing results. Stream quality improved rapidly following cha inel flushing by storm flow. Organic loading by tree litter can exert significant control on water composition, especially during low flow.Previous studies have demonstrated impaired water quality resulting from dissolution of leaf litter in pooled streams. The present report relates quality changes in a small stream to the quantity of leaf fall from riparian vegetation. A concurrent study of water-quality effects of tree leaves in laboratory tanks helps to interpret the field observations.The autumn shedding of leaves from deciduous forests may produce organic loading of otherwise unpolluted streams. The annual chemical quality cycle in small streams such as the North Fork of Quantico Creek may be generalized as low concentrations of solutes during the relatively high stream flows in winter and spring when runoff predominates over ground water inflow, middle values of solute concentration in summer showing the relative increase of ground water over runoff, and high concentrations of solutes during the autumn when most of the flow derives from ground water. Streams are at annual low flows in autumn over much of the United Slates, and the dissolved solids concentration is normally the highest for the rear. During the autumn lov, flow period, the capacity oí streams to assimilate organic material also is lower than at any other time of year. Depletion of dissolved oxygen ny decomposing litter often results in fid. kill., de-creases in bottom fauna, and m nuisance rdors from tinaeiohic decomposition. The mass of material Use'1 causes aes'het-v ueterao! "Po". and water treatment yobiems, clogging of water '•'e. tm.eiit filters in oarticulnr.OOciac , . Technology

Effects of water loss on primary production: A landscape-scale model

“…Because of the numerical abundance of first and second order streams, large drainage systems undergo cycles of expansion and contraction as discharge increases and decreases in headwater areas over the course of a year (Blythe and Rodda, 1973;Stanley et al, 1997). In short, the ebb and flow of water means that habitat availability changes over time, and the potential importance of biological processes may similarly become magnified or weakened as flow declines or rises (Slack and Feltz, 1968;Grimm and Fisher, 1992). The magnitude of change is often substantial in the Sycamore Creek drainage; 10 fold differences in wetted channel length can occur in a single year.…”

Characteristics of softwater streams in Rhode Island. I. A comparative analysis of physical and chemical variables

“…The significant negative correlation between pH and current velocity in streams B and C in this study indicates an effect of acid precipitation, which is estimated to have an average pH of 3 .5-4 .8 in New England (Cogbill, 1976 ; . Another factor which seasonally could have decreased the pH in these streams is leachate from allochthonous leaf material, as noted in other systems (Slack & Feltz, 1968) .…”

Hydrogeology of, and quality and recharge ages of ground water in Prince William County, Virginia, 1990-91

“…Accumulation of manganese in tree leaves by metabolic activity has been documented (Hem, 1985, p. 86). Slack and Feltz (1968) showed that fallen leaves had an effect on manganese concentrations in a small stream in Virginia during certain times of the year. Elevated concentration of manganese can form dark red, brown, or black stains on plumbing fixtures.…”