Water table fluctuations in the riparian zone: comparative results from a pan-European experiment

TLDR: The Nitrogen Control by Landscape Structures in Agricultural Environments project (NICOLAS) as discussed by the authors studied water table levels, hydraulic gradients and flow patterns within the riparian zone.

About: This article is published in Journal of Hydrology.The article was published on 2002-08-30 and is currently open access. It has received 174 citations till now. The article focuses on the topics: Riparian zone & Riparian forest.

Figures

Fig. 1. Location of the NICOLAS study sites.

Fig. 3. Average water table elevations by row at the French grass site, April 1998–December 1999. Data for row 2 have been omitted since they are very similar to row 1.

Fig. 6. Water table profiles, averaged by row, for the Romanian forest site, spring and summer 2000.

Fig. 7. Average water table elevations by row at the Spanish site, May 1998–December 1999. Data for row 2 have been omitted since they are very similar to row 1.

Fig. 12. Maps of water table elevation at the French grass site for selected dates in the autumn and winter of 1998–1999; the ground surface elevation for the site is also shown.

Fig. 2. Layout of the dipwell grid at each site.

Frequently asked questions

Q1. What have the authors contributed in "Water table fluctuations in the riparian zone: comparative results from a pan-european experiment" ?

This paper presents data collected as part of a pan-European study of nitrate buffer zones, the Nitrogen Control by Landscape Structures in Agricultural Environments project ( NICOLAS ). An identical experimental design was employed at each site, allowing riparian zone hydrology and nitrogen cycling processes to be explored across a wide range of temperate climates ; only the hydrological data are discussed here. All the riparian zones studied displayed a clear annual cycle of water table elevation, although other factors seemed equally important in influencing the range of variation. 

Q2. What are the future works mentioned in the paper "Water table fluctuations in the riparian zone: comparative results from a pan-european experiment" ?

This influence is not confined to flood events, but in summer may extend for long periods of time when there is little or no discharge from adjacent slopes. 

Q3. What is the role of the soil in regulating the water table?

The very existence of a floodplain is crucial in providing a low hydraulic gradient; soil hydraulic conductivity is also important in optimising soil water residence times within the riparian zone (see below). 

Q4. What is the optimum soil profile for a wetland?

The soil profile within the wetland consists of an organic upper horizon, a clay–silt horizon with ferrous oxidation spots and a deeper inorganic horizon of fine clay resulting from weathering of the schist substrate. 

Q5. What is the main focus of process studies of floodplain hydrology?

Most process studies of floodplain hydrology have focussed on bank storage, emphasising the attenuation of the flood wave, rather than the dynamics of thewater table. 

Q6. What is the effect of nitrate removal on the riparian zone?

Nitrate elimination occurred at most sites with an efficiency of 5–30% m21 reduction in nitrate concentration, and mostly within the first few tens of metres of the upland–wetland interface. 

Q7. What is the way to control water table in headwater tributaries?

In headwater tributaries, where floodplains are relatively narrow, soil moisture conditionswithin the floodplain will be predominantly controlled by runoff from the upslope catchment, not by fluxes from the river to the floodplain. 

Q8. What is the effect of the topography of the site on the water table?

The topography of the site and the low hydraulic conductivity of the soil means that it soon becomes saturated in the autumn, and the water table then remains close to the surface throughout the winter; only upslope does the water table remain deeper below the surface. 

Q9. Why does the water table not remain close to the soil surface for long?

Most importantly, because of the influence of the slope, the water table does not remain close to the soil surface for very long at either site, thus limiting the potential for denitrification to take place. 

Q10. How does the water table in the French grass site change in the summer?

it seems that hillslope runoff, plus rainfall, is sufficient to sustain soil saturation within the wetland throughout the summer so that the water table falls by only a few centimetres at most. 

Q11. What is the water table on a slope?

On such slopes, the water table tends to vary uniformly up the slope, remaining more or less parallel to the ground surface throughout the year, regardless of depth. 

Q12. What is the definition of a functional riparian zone?

A functional riparian zone depends on the existence of topographic and soil conditions that conduce, at least seasonally, a high water table. 

Q13. What is the role of riparian zones in the study?

These NICOLAS results will be critical in investigating the potential of riparian zones to act as nitrate buffer zones, limiting the movement of nitrate pollution from farmland into surface watercourses. 

Q14. What is the significance of riparian corridors?

Forman and Godron (1986) emphasise that, not only do riparian corridors occupy a distinct topological position within the landscape, but they also represent a distinct process domain. 

Q15. What is the average nitrate concentration in the water?

Fertiliser application rates are high, about 200 kg N ha21 yr21, which has resulted in elevated groundwater nitrate concentrations ranging from 10 to 20 mg N l21. 

Q16. What is the effect of a high water table on the slope?

A combination of high water table and high hydraulic gradient on the slope during winter generates significant subsurface flow into the riparian zone. 

Q17. What is the pattern of response in the riparian wetland?

Where the riparian water table is controlled in part by water level in the adjacent river or lake, a ‘hinged’ pattern of response is evident.