Near‐saturated surface soil hydraulic properties under different land uses in the St Denis National Wildlife Area, Saskatchewan, Canada

Abstract

Abstract:Surface soil hydraulic properties are key factors controlling the partition of rainfall and snowmelt into runoff and soil water storage, and their knowledge is needed for sound land management. The objective of this study was to evaluate the effects of three land uses (native grass, brome grass and cultivated) on surface soil hydraulic properties under nearsaturated conditions at the St Denis National Wildlife Area, Saskatchewan, Canada. For each land use, water infiltration rates were measured using double-ring and tension infiltrometers at 0Ð3, 0Ð7, 1Ð5 and 2Ð2 kPa pressure heads. Macroporosity and unsaturated hydraulic properties of the surface soil were estimated. Mean field-saturated hydraulic conductivity K fs , unsaturated hydraulic conductivity at 0Ð3 kPa pressure head, inverse capillary length scale ˛ and water-conducting macroporosity were compared for different land uses. These parameters of the native grass and brome grass sites were significantly p < 0Ð1 higher than that of the cultivated sites. At the 0Ð3 kPa pressure head, hydraulic conductivity of grasslands was two to three times greater than that of cultivated lands. Values of˛were about two times and values of K fs about four times greater in grasslands than in cultivated fields. Water-conducting macroporosity of grasslands and cultivated fields were 0Ð04% and 0Ð01% of the total soil volume, respectively. Over 90% of the total water flux at 0Ð06 kPa pressure head was transmitted through pores >1Ð36 ð 10 4 m in diameter in the three land uses. Land use modified near-saturated hydraulic properties of surface soil and consequently may alter the water balance of the area by changing the amount of surface runoff and soil water storage.

Drought impacts on Canadian prairie wetland snow hydrology

“…Basin snowmelt runoff was much lower during the severe drought periods, approximately 45-65 mm less compared to that in the normal periods. Snowmelt runoff was particularly low in 2000-2001 and this is related to the formation of macro-pores in dry soils (van der Bodhinayake and Si, 2004).…”

“…This relatively high runoff efficiency is due to wind redistribution of snow to streams, wetlands, depressions, and other contributing areas, relatively impermeable frozen soils during snowmelt and low cold season evaporation rates (Gray et al, 1986). The quantity of water in a wetland is governed by both surface and subsurface hydrological processes and is very sensitive to changes in soil and land cover conditions (van der Bodhinayake and Si, 2004). Upland wetland recharge is associated with water received from snowmelt and snowmelt runoff to the wetland from its surrounding basin.…”

Long-Term Water Level Changes in Closed-Basin Lakes of the Canadian Prairies

“…Permanent grass cover in the prairie region has been shown to increase infiltration and decrease runoff as compared to cultivated land (van der Kamp et al, 2003;Bodhinayake and Si, 2004). Hence the land-cover change from native prairie grass to cultivated land during the twentieth century would, by itself, be expected to have led to an increase of surface runoff and an increase of lake levels.…”

Loss of Playa Wetlands Caused by Reclassification and Remapping of Hydric Soils on the Southern High Plains

“…Watersheds in grassland have a higher infiltration rate relative to cultivated areas (van der Kamp et al 2003) due to increased vegetation slowing water flow rates. In addition, both an increase in the density of macropores occurring as a result of root channels (Mapa and Gunasena 1995) and soil fauna increase hydraulic conductivity (Lepilin 1989;Bodhinayake and Si 2004). Moreover, organic content is typically greater in grasslands, leading to higher aggregate stability, primarily after decomposition is initiated and by products of microorganisms and mycelia have formed (Mapa and Gunasena 1995).…”