Reforestation Influences on Small Watershed Streamflow

Abstract

Analysis of flow duration curves showed that reforestation of a 44-acre watershed near Coshocton, Ohio, reduced flow in the low flow tail of the curve but did not significantly reduce flows above 0.25 inch per day. Other analyses showed that reductions also. occurred in the maximum annual flow volumes for all periods of flow durations of I day or longer. The onset of dormant season flow was significantly delayed. Data from a 43.6-acre watershed at the North Appalachian Experimental Watershed have been the subject of several analyses during the past decade. About 70% of this watershed was reforested to pines in 1938 and 1939, whereas the remainder was left in uneven age hardwoods. The latest analysis [Ricca et al., 1970] con-ß ß ß ß ß REFORESTED ! o o o Oß ß o ß ß o 000 ß ß ß O0 ß ß 0 ß ß ß 0 CLIMATIC INDEX • oO oo ß 0-0 -ß • ß ß ß O• ß •-O0 q• ß _ ß REFORESTED (ADJUSTED) 1542-A, 1959. Tennessee Valley Authority, Division of WaterControl Planning, Hydraulics Data Branch, A brief history of watershed research in TVA, 2'9 pp.,

Waters and forests: from historical controversy to scientific debate

“…Among many other studies, we can cite the one by McGuinness and Harrold (1971), who studied the impact of reforestation on the floods in a small watershed, and compared the frequency distribution of the floods before and after reforestation, to conclude that for the rarest events, the impact of reforestation was either slight or nil. A similar conclusion was reached by Robinson et al (1991) in Germany, by Cosandey (1993) in southern France, and by Beschta et al (2000), who considered that for return periods longer than 5 years, the impact of forest exploitation was of the same order of magnitude as the discharge measurement uncertainty.…”

“…Several examples illustrate this general statement: † In the Three Bar deforestation experiment, Hibbert (1971) showed that the eradication of chaparral cover had turned ephemeral watersheds into perennial ones, which shows that deforestation increases low flows. † In the Coshocton reforestation experiment, McGuinness and Harrold (1971) reported that the low flow difference between the reference and the treated watersheds increased with time, i.e. that reforestation led to a reduction of low flows.…”

“…Hornbeck et al (1997) showed that this earlier melt could result in decreased flood peaks. † Resumption of flow: in Coshocton, McGuinness and Harrold (1971) showed that the reforestation of watershed 172 had, after 30 years, resulted in a 1-month delay of the date by which a given percentage of the flow had passed through the outlet. Their interpretation was that the soil needed a longer recharge period when depleted by forest trees.…”

Forest Bioenergy Feedstock Harvesting Effects on Water Supply

“…47 Removal of the forest cover drastically reduced oceanic fog interception, which was a major component of precipitation input, and thus produced a decline in annual water yields. In most cases, water quantity declines after forest harvesting are the result of type conversions or reversions such as agriculture to forest 48 or grassland to Pinus spp. or Eucalyptus spp.…”

“…Several investigators have concluded that except for unusual storm events, harvesting and reforestation do not result in significant increases in peakflows. 15,46,48 Some combinations of terrain, geology, soils, vegetation, and climate may combine to create localized hazards.…”