Characterising the Surface Hydrology of Prairie Droughts

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1 QdroD QdfoD Qdro Qdfo SunMax C:\ Program Files\ CRHM\ Qsi global CalcHr t rh ea u p ppt Qso Qn Qln SunAct form_data calcsun Qsi hru_t hru_rh hru_ea hru_u hru_p hru_rain hru_snow hru_sunact hru_tmax hru_tmin hru_tmean hru_eamean hru_umean hru_rhmean hru_newsnow obs net_rain net_snow intcp_evap intcp net cum_net netall Rn Qg Qs net_rn hru_evap transp_on evap Characterising the Surface pb Hydrology of Prairie Droughts John Pomeroy, Kevin Shook, Robert Armstrong, Xing Fang Centre for Hydrology University of Saskatchewan Saskatoon, Sask

2 Prairie Hydrology Major river flow (SSR, NSR) is primarily from mountain runoff, but prairie runoff supplies smaller rivers, streams, wetlands, and lakes Prairie Runoff forms in internally drained (closed) basins that are locally important but non-contributing to river systems that drain the prairies, OR drains directly to small prairie rivers (Battle, Souris, Assiniboine) >80% of runoff during snowmelt period Redistribution of snow to wetlands and stream channels in winter is critical to formation of runoff contributing area Drainage of small streams and wetlands ceases completely in summer when actual evaporation* consumes most available water. Prairie streams are almost completely ungauged and often altered by dams, drainage, water transfers, etc *evaporation used here as transpiration + evaporation + sublimation

3 Non-Contributing Areas to Streamflow a Prairie Characteristic

4 Prairie Runoff Generation Snow Redistribution to Channels Spring melt and runoff Dry non-contributing areas to runoff Water Storage in Wetlands

5 Prairie Hydrology don t blink Smith Creek, Saskatchewan Streamflow m 3 per second Drainage area ~ 450 km 2 Average High Year 2000 Low Year No baseflow from groundwater 27-Dec 27-Nov 28-Oct 28-Sep 29-Aug 30-Jul 30-Jun 31-May 01-May 01-Apr 02-Mar 31-Jan 01-Jan Hydrological drought can be viewed as the absence of prairie runoff

6 Sparse Prairie Streamflow Network Suitable for Drought Analysis Burn et al., 2008 Inadequate coverage to characterise prairie runoff

7 How to Characterise Hydrological Drought for the Prairies? River flows well gauged, but subject to abstraction, storage and do not reflect Prairie hydrological conditions. Streamflow network is more representative but is sparse, and subject to changes in land use (drainage), abstraction, storage. Existing indices considered inappropriate. Possibility to model prairie runoff generation and related hydrological processes to create a hydrological drought surface for the Prairies using atmospheric data.

8 Cold Regions Hydrological Modelling Platform: CRHM Modular purpose built from modules Modules physically based algorithms derived from +45 years of prairie hydrology research at Univ of Saskatchewan Hydrological Response Unit (HRU) basis natural landscape units with horizontal interaction, ponds, no need for stream HRUs assumed internally uniform, basis for coupled energy and mass balance HRUs connected aerodynamically for blowing snow and via dynamic drainage networks for streamflow Incorporate wetlands directly in drainage system

9 CRHM Module Development DATA ASSIMILATION Data interpolation from station or grid to HRUs SPATIAL PARAMETERS Basin and HRU parameters are set. (area, latitude, elevation, ground slope, aspect) PROCESSES Infiltration into soils (frozen and unfrozen) Snowmelt (prairie & forest) Radiation level, slopes Evapotranspiration Snow transport Interception (snow & rain) Sublimation (dynamic & static) Soil moisture balance Wetland water balance Sub-surface runoff Routing (hillslope & channel)

10 CRHM Drought Hydrology Simulation Model the effects of local drought meteorology on the hydrology of representative, first-order prairie basins Create virtual basin models, which can be applied to gridded datasets Allows comparison of basin response to drought conditions and to normal variability Requires high resolution driving data over entire Prairies for normal ( ), non-drought ( ) and drought periods ( ) Snowfall, rainfall Incoming shortwave radiation, cloudiness or sunshine hours Temperature Humidity Wind speed

11 Modelling Objectives To Demonstrate the: differences between drought and non-drought hydrological cycling at the surface, evolution of hydrological drought over time and space Calculated Variables as ratios to non-drought conditions (~Hydrological Drought Indices~) Snow Accumulation Spring Runoff Actual ET/PET peak SWE, duration total, duration growing season

12 CRHM Prairie Hydrological Model Configuration Flow Chart in Cold Regions Hydrological Modelling Platform (CRHM)

13 CRHM Tests Creighton Tributary of Bad Lake -well drained semi-arid St. Denis National Wildlife Area -internally drained subhumid

14 CRHM HRU Configurations Well Drained Poorly Drained Fallow Stubble Cultivated Grass Coulee Wooded Wetland Stream Pond Creighton Tributary, Bad Lake Wetland 109, St Denis

15 Creighton Tributary Water Balance % Summer Fallow 55% Stubble 15% Grassland Coulee Fallow Stubble Fallow Stubble Coulee Basin Coulee mm water equivalent Snowfall Rainfall Runoff Sublimation Drifting Snow Evaporation

16 Snowmelt Runoff for Creighton Tributary No calibration

17 Snow Accumulation at Wetland 109, St Denis

18 CRHM Hydrological Indices Surfaces Snowcover duration Peak SWE Spring discharge amount Streamflow duration AET/PET