The use of ‘rock hard’‐sodium sulphate tablets for quickly determining preferential water flow routes in soils

Abstract

Subsurface water flow routes have been inferred from gypsum sphere weight loss with minimal disturbance to soil structure or flow nets (Crabtree and Trudgill, 1984). This technique is limited by the relatively slow, fixed dissolution of gypsum. A solution is to use tablets consisting of Durham's 'Rock Hard Water Putty' and sodium sulphate. Laboratory tests indicate that tablet dissolution is controlled by the ratio of Rock Hard to sodium sulphate and is proportional to net throughflow yet independent of throughflow pH (between 3.0 and 9.0) and throughflow rate (at rates < 0.04 1 hr-l). The tablets are also mechanically stable, economical, and environmentally safe. Field study results using the Rock Hard-sodium sulphate tablets are consistent with both the laboratory findings and the results of previous investigators.

Riparian influence on hyporheic‐zone formation downstream of a small dam in the Blackland Prairie region of Texas

“…The spheres were prepared according to Renshaw (1988), poured into glass moulds and dried at 55°C for 3 days. Spheres were buried in nylon mesh at four distances in the riparian zone: 4, 8, 12, 16 m from the stream.…”

“…Subsurface groundwater flow (SSF) from upland regions and infiltration gains were measured using the gypsum sphere mass-transfer method based on Crabtree and Trudgill (1984) and modified by Renshaw (1988) for quick determination of preferential water flow in soils. The spheres were prepared according to Renshaw (1988), poured into glass moulds and dried at 55°C for 3 days. Spheres were buried in nylon mesh at four distances in the riparian zone: 4, 8, 12, 16 m from the stream.…”