Thanos Papanicolaou
IIHR - Hydroscience & Engineering, The University of Iowa

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Application Note: Watershed Studies
 
Watershed dynamics: Many watershed simulations today work in the batch world; an event is simulated based on a static set of field data.  If newer data become available, the simulation is simply rerun. For example, hydrodynamic and sediment transport simulations to predict geomorphologic changes within a stream and the impact of these changes to the aquatic life are conducted by considering a constant sediment input value from terrestrial sources such as roads, floodplains, and other natural occurring disturbances (i.e., landslides, fires).  As a result perturbations that exist in the system due to the spatial and temporal variability in the terrestrial sediment input are not accounted.  Very few applications use real time data even if the capability to do so is available.  A great effort has been recently devoted to run simulations faster than real time based on static data sets.  However, this is highly inefficient and leads to multiple sediment predictions that are conflicting when major events are predicted.  This lack of ability to dynamically inject data into simulations and other applications, as these applications execute, limits the analysis and the predictive capabilities of these applications.  The novel capabilities to be sought here are application simulations that can dynamically accept and respond to on-line field data and measurements and/or control such measurements.  This synergistic and symbiotic feedback control-loop between simulations and measurements is a novel technical direction that can open domains in the capabilities of simulations within watersheds that can facilitate the “capturing” of episodic catastrophic events. 
   

Development of a watershed testbed: The Clear Creek Watershed (CCW) drains approximately 250 km2 to the Iowa River, which is a tributary to the Mississippi River, and is well suited for multi-process observations at various scales.  For almost 20 years, the CCW has been a USDA/NRCS testbed for conservation improvements to reduce soil erosion from agriculture.  The CCW and the Iowa River Basin together constitute the primary sources of Total Phosphorus (TP) and Total Dissolved Phosphorus (TDP) in the Upper Mississippi River Basin.  The unique circumstances leading to the current state of the watershed make the CCW an ideal site to study the effects of human intervention on the natural landscape, i.e., the watershed has become a scientific “hotspot.”  Moreover, CCW is a dynamic landscape with ubiquitous heterogeneity in its surface terrain.  The presence of concave and convex hillslopes affects the spatial and temporal scales of pollutant transport from the source area to the outlet of the watershed.  The high erosion rates in the CCW result from a combination of swelling and highly erodible soils with steep gradients and intensive agricultural use.

  In particular, the South Amana sub-watershed (SAW) (~26 km2) of CCW has recently been selected by the NSF as one of the eleven test bed prototypes for comprehensive research using a wide-range of instruments, data, and multi-disciplinary simulation models integrated in watershed-scale environmental observatories known as digital observatories (DO).  The SAW provides a remarkable natural laboratory for investigating problems of fundamental scientific interest such as severe anthropogenically-triggered erosion and identification of non-point sources from different agricultural activities.  Extensive biogeochemical and ecohydrological data are available for the sub-watershed as well as detailed information on land use and management practices.  The SAW is the only watershed in the State of Iowa where detailed, updated documentation of the different land uses with a known rotational pattern and management practices is available at the plot scale per season over a period of at least 50 years.