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Hydrological processes, nutrient and soil loss in small agricultural catchments, models and the WFD

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What is so special with hydrology in small catchments when compared to larger ... is the winter, with freezing soils, snow development and freeze/thaw cycles ... – PowerPoint PPT presentation

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Title: Hydrological processes, nutrient and soil loss in small agricultural catchments, models and the WFD


1
Hydrological processes, nutrient and soil loss in
small agricultural catchments, models and the WFD
Johannes Deelstra Bioforsk, Norway.
2
What did we do and why?
  • What is so special with hydrology in small
    catchments when compared to larger catchments?
  • Is hydrology in countries in Northern and Western
    Europe different from that in Southern Europe?
  • Do smaller catchments need any special
    consideration when considering hydrology, soil -
    and nutrient losses?

3
Location of catchments
Agricultural environmental monitoring programme
(JOVA), similar programs in Latvia and Estonia
Quantifying runoff, nutrient and soil loss
Catchments represent different agricultural
practices and climate
4
Some catchment characteristics
5
Runoff and nutrient loss
6
Characteristic for runoff generation is strong
seasonality in runoff
During growing season very little runoff
7
Especially for Norwegian catchments, yearly
runoff and nutrient loss is generated in only
limited number of days
An example for the Skuterud catchment, Norway
8
Subsurface drainage and nutrient and soil loss
Subsurface drainage systems contribute
significantly in nutrient loss
9
Characteristic for many catchments is the large
in-day variation in runoff
10
This variation can be expressed through a
flashiness index, showing the rate of change
- based on average daily discharge values - based
on hourly discharge values (in-day variation)
day
hour (in- day variation)
11
Which factors might affect runoff generation?
  • The size of the catchment is important
  • In addition are soil types important
  • The share of agricultural land is important
  • It is believed that subsurface drainage systems
    have a significant influence on runoff generation

12
Runoff generation, scale and subsurface drainage
Has subsurface drainage an impact on soil loss?
13
Runoff generation processes
  • In humid, temperate climates, surface runoff is
    often generated through saturation from below
  • One of the reasons for subsurface drainage
    systems in many European countries is to drain
    excess water from the rootzone, thereby
    preventing surface runoff
  • In this case also erosion generation processes
    need special consideration
  • Especially in small catchments, large variation
    in runoff over short time periods occur, this
    most likely having a large effect on nutrient and
    soil loss (energy)
  • An additional aspect to be taken into
    consideration is the winter, with freezing soils,
    snow development and freeze/thaw cycles
  • To be able to give advice on best management
    practices, among others simulation models,
    capable to these handle processes are needed.

14
Do we have models to deal with those situations
  • Several models are testet in a Norwegian
    catchment
  • SWAT (water balance, nutrient and soil loss)
  • The SWAT model has also been applied in Norway as
    part of EuroHarp and Striver, two EU projects
    (large scale)
  • The model is tested now in Skuterud
  • DRAINMOD, developed at NCSU (Skaggs) simulating
    subsurface drainage/surface runoff/nitrogen
    dynamics
  • HBV model (hydrology)
  • INCA model (hydrology, nutrient dynamics)
  • SOIL/SOIL_NO and COUP (hydrology,nitrogen) have
    been tested (developed by SLU)
  • WEPP (Water erosion prediction model) tested on
    small plots

15
Hydrological processes, nutrient and soil loss in
small agricultural catchments, models and the WFD
  • Only when we have models which simulate the
    dominating flow generating processes and there
    affect on nutrient and soil loss under our
    prevailing climatic conditions we can be
    successful in implementing the WFD
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