Forested Basins Research Articles

The output of sediments and solutes from forested and cultivated clayey drainage basins in Luxembourg

AbstractThe output of material from 11 small drainage basins in the Keuper region of central Luxembourg is considered. Attention is given to differences between forested and cultivated basins. Whilst the output of suspended solids from the cultivated Mosergriecht catchment may be as much as five times higher than from the forested Keiwelsbaach, the solute load is only 50 per cent and the runoff 20 per cent higher. Relationships between dispersed clay in suspension and the water chemistry observed for the forested drainage basins are not present in the cultivated catchments. Water having a milky appearance and containing dispersed clay is of more frequent occurrence in forested basins where subsurface runoff occurs in macropores and cracks in the undisturbed soil.

Effect of Clear‐Cut Silviculture on Dissolved Ion Export and Water Yield in the Piedmont

A paired watershed experiment in Putnam County, Georgia, was carried out from 1973 to 1980 to determine the effects of a typical southern clear‐cut operation on water quality, timing, and yield. This report shows that increases in monthly exports of dissolved N, P, K, Ca, Mg, Na, TKN, and total electrolytes were short‐lived and less than 0.5 kg ha−1 month−1 and may therefore be considered minor for practical purposes. Stream water concentrations were mostly diluted by clear‐cutting, but a monthly water yield increase of 1 to 2 cm flushed an extra 0.15 kg ha−1 month−1 of nitrate‐nitrogen from the basin during a 2‐year period following harvest. Twenty surrounding forested basins (7 to 165 ha in area) were sampled monthly for 1 year, showing that the experimental pair was representative of the general levels of dissolved ions in forested Piedmont streams. Results suggest that clear‐cut silviculture in this region will neither reduce soil fertility by flushing ions into streams nor eutrophy stream water.

Study on the Behavior of Soil Moisture in Natural Forest Basin

Study on the Behavior of Soil Moisture in Natural Forest Basin

BEHAVIOR OF SUBSURFACE WATER IN A HEADWATER BASIN IN THE TAMA HILLS

The research on the three-dimensional behavior of subsurface water during and after a rainstorm throughout a small forested basin (0.56 ha) was carried out in the Tama Hills. The basin is located in the northeastern part of Kanagawa Prefecture, Japan and composed of flat valley bottom (mean gradient of 10°) and steep side slopes (mean gradient of 25°). Twenty four borings were practiced to know soil profiles and depths to the Tertiary bed rock (mudstone) from the ground surface. As the results, soil profiles were classified as A-horizon, B-horizon, transported soil layer, weathered zone of bed rock and bed rock. Depths to the bed rock were about 3 to 4m in the valley bottom and 1.5 to 2m in the middle parts of the side slopes. The ancient V-shaped valley on the bed rock and its weathered zone were buried by the transported soil, and the present geomorphic feature was formed over. The transported soil is composed of loam and masses of weathered bed rock and assumed to be carried from upper parts of the side slopes. Fifty-six observation wells, being classified into Wells D and Wells S, were installed through-out the basin. The Wells D were dug to the top of the bed rock and used to observe the behavior of the “deep groundwater body”. On the other hand, the Wells S were dug to about 1m below the ground surface and used to observe the behavior of the “shallow ground-water body”. In order to characterize vertical distributions of soil-water pressure head in response to rainstorms, forty tensiometers were equipped at five sites. Three rainstorms with a total rainfall of more than 100mm occurred during an observation period from September 28 to October 21, 1979. The major results clarified by this research are as follows: 1. The impermeable layer, the top of which is generally about 1m below the ground surface, is found almost over the basin. This layer plays important roles in building up the temporal shallow groundwater body and confining the deep groundwater body during and shortly after the rainstorms. 2. The impermeable layer is not found both in a lower part of the valley bottom and in vicinity of the ridge top. A lack of the impermeable layer in vicinity of the ridge top may affect the behavior of the deep groundwater body during the rainstorms. The rainwater brought on this part is expected to cause a quick response of the piezometric surface of the deep groundwater body to the rainstorms and make the piezometric surface rise about 10cm above the ground surface in some wells. 3. A temporal saturated zone is formed in the A-horizon during and shortly after the rainstorms and discharges into the stream channels, making an important contribution to stormflow generation. There is a strong possibility of application of the results to other headwater basins in the Tama Hills, and therefore more similar researches must be carried out from viewpoints of disaster prevention and geomorphological evolution.

Differences in the Behavior of Soil Moisture During Rainstorm between Natural Forest Basin and Urbanized Basin

Differences in the Behavior of Soil Moisture During Rainstorm between Natural Forest Basin and Urbanized Basin

WATER RESOURCES APPLICATIONS OF STREAM CHANNEL CHARACTERISTICS ON SMALL FORESTED BASINS1

ABSTRACT. Stream channel characteristics were found to be useful indices to the hydrology of 27 small forested basins in the Northeast United States. Channel width alone explained 37 percent of the variation in mean annual runoff, whereas channel width combined with basin area explained 78 percent of the variation in mean annual runoff. This approached the percentage of variation in mean annual runoff explained by mean annual precipitation (83 percent). A simulated 15% increase in precipitation, such as might occur in a weather modification project, produced increases in channel width, depth, and channel area of 3, 4, and 8 percent, respectively.