Model Instance Title:
Nene sediment transport for Phosphate re-mobilisation  
Model Instance Short Name:
Nene Phosphate  
Description:
This modelling was undertaken for the UK Environment Agency on sediment and phosphorus dynamics in the main six Water Framework Directive (WFD) water bodies of the River Nene in eastern England. The sampled water bodies started in the head waters of the Nene near Daventry (water body 1) and continued to the Dog in Doublet lock to the east of Peterborough (water body 6). Catchment erosion rates, river inputs and transport through the six water bodies were examined using the Caesar Desc Platform (CDP) landscape evolution model and compared to reported literature values. The CPD model gave first order estimations of natural baseline catchment erosion of ~0.5 t km2 yr-1. However, human impacts on erosion such as land drainage are not included within this estimate. Therefore, literature erosion rates were identified, with the most robust catchment erosion rate being ~6.6 t km2 yr-1. Using output variables calculated from the CPD model we applied these to this value to give a range of likely erosion and transport for each of the six water bodies based on typical annual precipitation rates. It was calculated that between 1000 and 10000 tonnes sediment would pass through the end of water body 6 (Dog in Doublet) each year. Water body 5 had the greatest quantity of sediment leaving it whilst greatest sediment deposition occurred in water body 6. Sediment associated TP and OEP transport and deposition corresponds to these sediment movements as well as their respective concentrations in the sediment. It was calculated that between 4 and 42 T of TP and 0.074 and 0.69 T of OEP attached to sediment passes through the exit of water body 6 each year, either as suspended sediment or bedload. Water samples were analysed and a strong correlation found between SRP and Boron, suggesting that SRP in the river waters at the time of sampling had a strong sewage treatment works (STW) signature. With EPC0 results suggesting that river sediments are currently active sorbents of SRP, the presence of sediment is likely acting to decrease the SRP in the river water. Thus, the greatest management task to improve water quality with respect to the concentration of SRP is preventing the sediment becoming a source of SRP if the river water concentration falls below the EPC0 concentration. This may represent a balance between de-silting (although this would involve removing a SRP sink), the harvesting of macrophytes to remove P in the biomass and a continued decrease in P inputs from Sewage Treatment Works in addition to Catchment Sensitive farming approaches to reduce diffuse P inputs  
Creation/Publication Date:
2013  
Keywords:
Hazards Floods   
Others Fluvial sediments  Phosphates   
 
Disciplines:
GROUNDWATER SCIENCE   
Contact Details:
NameOrganisationCountryEmail
Andrew Barkwith   British Geological Survey   UK   andr3@bgs.ac.uk  
 
Model Code Name:
Time Interval Covered:
from: 01-Jan-1962   to: 31-Dec-2002
Spatial Extent:
Bounding Box (Lat/Long WGS84):
West: -1.223   East: -0.214   South: 52.164   North: 52.675  
Scope of Vertical Extent: Superficial  
Vertical Extent (metres above OD) Maximum: �   Minimum: �    
Spatial Reference Systems of Datasets:
Horizontal Reference System: WGS 84
Vertical Datum: mean sea level height
Vertical Units: metre
Grid Resolution:
Spacing XSpacing YSpacing ZCells XCells YCells Z
200   200     338   290    

Time step interval: variable   Time step value: �
Additional information (science questions addressed, assumptions etc.):
Boundary Condition   No-flow along all boundaries except river mouth, where it is a surface water outflow  
Initial Condition   Gridded ASCII of Sediment size distribution  
Initial Condition   Gridded ASCII of Surface Elevation  
Initial Condition   Gridded ASCII of Near Surface Soil Storage  
Initial Condition   Gridded ASCII of Soil Moisture Deficit  
Initial Condition   Gridded ASCII of Groundwater levels  
Science Question   Where along the river could legacy phosphates be stored or released?  
Science Question   How does the spatio-temporal distribution of fluvial sediment change within the Nene river catchment at the decadal scale?  
 
Data:
Input Dataset NameVersionURL LinkParameterValueUnits
Input Data - gridded ASCII          
    Daily Potential Evapotranspiration      
    Daily Rainfall      
    HOST      
    Landuse Type      
    Specific Yield      
    Hydraulic conductivity      
    Bedrock Elevation      
Output Dataset NameVersionURL LinkParameterValueUnits
Output Data - gridded ASCII (at 10 day intervals)          
    Elevation      
    Difference in elevation from initial conditions      
    Grounmdwater head      
    Baseflow contribution to surface      
    Near surface soil storage      
    Recharge to groundwater      
    River Flow      
    River velocity      
    Water depths      
    Cumulative bedload sediment flux from the catchmen      
    Cumulative suspended sediment flux from the catchm      
    Grain size distribution at each node      
 
Documents and Published Papers available for this model instance:
AuthorsTitleDate
Tye, A.M.; Hurst, M.D.; Barkwith, A.K.A.P.   Nene phosphate in sediment investigation - Environment Agency Project REF: 30258   2013