I CATENA vol. 14, p.439 451 Braunschweig 1987 USING CESIUM-137 TO ASSESS THE VARIABILITY OF NET SOIL EROSION AND ITS ASSOCIATION WITH TOPOGRAPHY IN A CANADIAN PRAIRIE LANDSCAPE L.W. Martz and E. de Jong, Saskatoon SUMMARY 1 INTRODUCTION Cesium-137 in the soil was used to es- There is substantial qualitative evidence timate net erosion in a small (178 ha), of serious wind and water erosion in the cultivated drainage basin in central Canadian Prairies, but little quantitative Saskatchewan. Net erosion over the past data on the magnitude and spatial dis- 20 to 25 years was estimated at 174 sites tribution of erosion (COOTE 1984, DE and ranged from a loss of 121 kg m -2 to JONG et al. 1983). The few available site a gain of 1197 kg m -2. Soil loss was most measurements of erosion are not gener- severe on slope crests and in swales while ally comparable as they are based on soil gain was greatest in upland depres- different techniques. Using admittedly sions and along the main outlet channel, crude techniques, COOTE (1984) esti- In a representative sample of 71 sites mates the average soil loss from crop- spaced regularly over the basin, 58% land in western Canada at 0.6 kg m 2 of the sites showed soil loss and 17% y-l Given that soil formation rates in showed soil gain. Computer programs Canada are usually less than 0.1 kg m 2 were developed to calculate topographic y-I (BIRD & RAPPORT 1986), such variables from a digital terrain model of erosion rates would cause very serious the basin. The relationship between net deterioration of the soil resource. erosion and topographic variables was One objective of this study was to ex- examined by grouping sites into land- amine the severity and variability of soil form categories. Both the group means erosion through a common agricultural and standard deviations of net erosion, landscape in the Canadian Prairies. The and the nature of within-group correla- amount of 137Cs in the soil was used tions of topographic variables with net to estimate net erosion at 174 sites in a erosion, differed between landform cate- 1.8 km 2 cultivated drainage basin. gories. Cesium-137 is a relatively long-lived 1SSN0341 8162 isotope (half-life 30.2 years) input to the atmosphere by nuclear explosions @1987 by CATENA VERLAG, D-3302 Cremlingen-Destedt, W. Germany and carried back to the land surface 0341 8162/87/5011851AJS$ 2.00 + 0.25 by precipitation (WISE 1980). The iso- CAI LNA An Inlerdis¢iplinar~ Journal of SOIL SCIENCk HYDROLOGY GEOMORPHOLOGY