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Since the first appreciation of the widespread occurrence of acid rain in North America (), most public attention has focused on the acid component rather than effects from the associated elements in atmospheric deposition. The emphasis has been on freshwater ecosystems and forests in sensitive regions with relatively low buffering capacity. Effects of acid deposition on coastal marine ecosystems have usually not been considered, which makes sense in the context of acidity. Marine ecosystems are very well buffered, since they contain large amounts of dissolved carbonate and bicarbonate, and consequently are quite insensitive to acid inputs. Similarly, marine waters contain huge quantities of sulfate (∼ 28 mM) and thus are not sensitive at all to inputs of sulfate associated with acid deposition. On the other hand, nitrogen (N) pollution can cause severe degradation in coastal marine ecosystems, and the role of atmospheric deposition as a contributor of nitrogen to coastal waters has received increasing scrutiny over the past 15 years since Fisher and Oppenheimer (1991) noted that the nitrate anion associated with nitric acid in acid rain may be a major source of nitrogen to Chesapeake Bay.

A gulf remains between the practical concerns of environmental managers and the research interests of most academic environmental scientists. There is a scarcity of published work that integrates the wider concerns of environmental managers with academic research into the hydrological and hydro-chemical functioning of catchments at different scales. This volume is devoted to attempts by those, mainly concerned with environmental management in practice at the local and regional scale, to see the headwater wetlands in their context. The main issue addressed is- if a headwater regions contains wetland, what are the implications of this fact for environmental management and how does the wetland affect the management of the basin as a whole.

The paper describes the first approach to wetlands mapping in headwater areas at the continental scale. Given the size of the minimum mapping unit it is evident that a class like wetlands is underestimated in the final assessment, as it is often characterized by objects smaller than 25 ha. It is known that this is a drawback affecting in particular the “water” classes of the CORINE classification. The following assessment has been carried out on the area covered by CORINE data, covering the EU15 Countries (excluding Sweden) plus Poland, Estonia, Latvia, Lithuania, Czech Republic, Slovakia, Slovenia, Hungary, Bulgaria, Romania, Bosnia and Herzegovina, Albania, Macedonia, for a total of 4,650,000 ha. Using a 250-meter resolution DEM, only headwater areas larger than 1 km are reported in the presented map of headwaters in south-western Europe. The process of mapping can be further developed by deeper characterising the identified areas, for example by assigning them to corresponding drainage basins, altitudinal areas, landscape or administrative units. The results are based on the data available. Updating and improvement will be possible in the short term with the delivery of the new CORINE 2000 system (based on satellite images acquired between 1999 and 2001) and using more detailed Digital Elevation Models (e.g. Shuttle Radar Topography Mission).

The worth of forest coverage is discussed by the comparison of both devastated and well-grown forested headwaters through sediment yields, flood control function, water budget and heat budget. Many hydrological and micro-meteorological observations from slopes to headwaters have been carried out in Japan, at hilly mountain underlain by weathered granite and other geology. In order to analyze the observed data and to explain the results, needed models have been developed. Finally, it has become clear that the worth of forest coverage emerges 50–60 years after initial reforestation. In headwater wetlands, the knowledge attained is effective for the explanation of the role and the planning of conservation.

The was proclaimed in 1978 to support the important role of local headwater catchments in water and soil conservation. However, an ecologically oriented watershed management had not been realised until 1990s. In the 1970–1980s, watersheds of the Jizera Mts. declined as a consequence of the acid atmospheric deposition (namely sulphate originate by lignite combustion), and commercial forestry practices (spruce plantations of a low stability, extensive clear-cut, heavy forest mechanisation, non-effective control of insect epidemics, and unsuccessful reforestation). Both run-off genesis and water quality in streams and reservoirs deteriorated. Particularly, the erosion of soil increased from 0.01 to 1,34 mm/year, and sediment run-off up to 30% of the soil volume eroded. In the surface waters, low pH values (4–5), high content of toxic metals (namely aluminium, 1–2 mg/l), extinction of fish and drastically reduced zooplankton, phytoplankton and benthic fauna were observed. A recent recovery of surface waters in the Jizera Mts. (an increase in mean annual pH values to 5–6, a drop in aluminium concentrations to 0.2–0.5 mg/l, successful reintroduction of brook char, ) results namely from the decreased air pollution (in the 1990s, the deposition of sulphate decreased to cca 40% in comparison with the year 1987), and from the stabilisation of forested wetlands by grass cover (at clear-cut areas, the leaf area index dropped from 18 to 3.5). After the clear-cut of spruce plantations, Junco effusi-Calamagrostis villosae became a new dominant community in headwater catchments of the Jizera Mts. During the period of 13 years, at the clear-cut slope of the Jizerka catchment, the composition of herb layer changed following increased moisture conditions. The Ellenberg's soil mosture index increased in each point of the investigated slope. Headwater pet-lands play an important role in fixing the free Al in organic complexes not toxic for fish.

Drainage of peat land results in drier soil cover and reduced evaporation. This, in turn, generates higher annual runoff. However, the main hydrological effect of mire drainage is related to changes in the pathways of water through the soil, not to the change in water balance. Mire drainage can contribute both to increase and reduce runoff peaks. Changes in runoff can occur both as a direct and an indirect effect. The direct effect depends on peat hydraulic properties, mire type, the hydrological situation and drainage intensity. Where the afforestation is successful a denser forest cover will indirectly lead to reduced storm runoff as evapotranspiration will increase. The snowmelt runoff will also fall due to decreased snow melting rates and less snow accumulation. Where the peat has low hydraulic conductivity, which is often the case with fens, the drainage will result in a relatively high ground water table, low water storage capacity and rapid runoff. On mires with a high fibre content, low density and degree of humification, the conductivity and storage capacity can be relatively higher and drainage will result in increased water storage and reduced flood peaks. As time passes after drainage, the peat hydraulic properties will become saturated due to compaction by subsidence and increased decomposition, which in turn causes the runoff to increase again.

The impacts of ditching depend on the type of mire in question. On fens with a supply of water from upland fields, ditching may increase runoff from the whole watershed by bypassing the runoff from an upland area faster than the fen would have done in its natural state. Ditching of bogs causes changes in runoff dynamics only from the peat land itself. During small rainfall events on unsaturated mires, a major part of rainfall is stored and the runoff is delayed. With heavy rainfall on saturated peat, drainage here can lead to faster runoff. Runoff peaks from snowmelt are higher on drained areas if the outlet before ditching was unable to carry the melted water and if the ditches are not blocked with snow and ice. Forest stands have a dampening effect on snowmelt runoff. The snow accumulation may be reduced by 30 % in forest stands compared to clearings. Snowmelt in dense forest stands is about 2 mm/degree day. In clearings, the snowmelt is in the range 3 to 6 mm/degree day, mainly due to increased albedo. In the Glomma watershed, drainage of forest area has probably not contributed to higher runoff rates and increased flood peaks, as only a smaller portion of the watershed has been drained and because the forest growth has increased due to the drainage effect. In smaller watersheds with a high proportion of drained peat lands, especially fens, the flood peaks are likely to have increased.

The processes of soil erosion and sedimentation may seriously affect mountain wetlands fed from surrounding upslope sources. In headwaters of the Jizera Mts., the potential annual loss of soil varies from 0.2 mm (mature spruce stands) to 1.2 mm (conversion to grass). Negligible sheet erosion has been observed at run-off plots covered by herbaceous layers. However, very important soil loss occurred in erosion rills originated by skidding of timber (from 0.3 to 1.2 mm/year). The critical parameter affecting the recovery of rills is their depth. The increasing depth of rills is related to a drop in both vegetation cover and number of species, and to a higher proportion of hemicryptophytes and plants forming clusters or bunches. These plants do not have a high potential to cover the soil surface, and to protect it against erosion. Thus, the process of soil erosion may be prolonged. The number of species (species richness) found in recovering rills increases significantly with the time (age of rills). From the point of view of soil protection, more shallow rills (depth from 0 to 0.25 m) can recover much better than only few deep rills (depth over 0.5 m). The shallow rills can re-grow quite fast, but in the deep rills, the spontaneous succession is very slow or even impossible. So, the rills deeper than 0.5 m require the application of reclamation techniques (stabilisation of the slope by check-dams etc.). It is evident, that environmental friendly forest practices may avoid the risk of soil erosion from the harvest of timber.

The concentration of nitrate and ammonium nitrogen in the groundwater was investigated one year before, and during seventeen years after, clear-cutting at the Pahalouhi experimental site at Kivesvaara, located in the middle-boreal coniferous forest zone in Finland (64°28 'N, 27°33 'E). The effect of natural regeneration of Norway spruce () and Scots pine () has been investigated at the same experimental site since 2002, when the Pahalouhi experimental field was supplemented with the inclusion of natural regeneration. All the treatments caused a rise in nitrate nitrogen concentrations, but leaching during the first two years from natural regeneration was clearly less compared with that observed following clear-cutting and planting. Having been initially virtually zero, the concentrations of nitrate nitrogen continued to rise for 5–7 years, reaching 500–700 μg/1 at their highest, after which they began to fall. The concentrations were still high seventeen years after clear-cutting, which constituted a situation not observed earlier. Compared with nitrate, there was no corresponding ammonium nitrogen leaching.

Runoff from peat land is supposed to be dominated by surface and near surface flows causing large flood peaks. However, Waunafon's degraded valley fen peat moorland includes organic layers up to 0.5m deep that are unsaturated in summer. So while, overland flow may be affected by rainfall onto saturated ponds, runoff in soil pipes, and through channel incised between the tufts of heath, this degraded peat land has a significant storage capacity in summer and commensurate capacity for seasonal flood attenuation.

Aspects of the hydrology of a small blanket peat catchment in Cloosh forest, County Galway, were investigated focusing on evapotranspiration during one calendar year in 1996, which was compared with the lysimetric values obtained from the nearest weather station. Using monthly rainfall data from the weather station and published data for through fall and stem flow, a value for the net amount of water reaching the soil was calculated. Runoff was measured using the STARFLOW recorder. It was found that the net effective water was equal to runoff in fully saturated blanket peat. The Penman-Monteith equation was used to calculate the evapotranspiration in the Cloosh catchment and this was compared the water balance equations. The change in the evapotranspiration values were attributed to the difference in through-flow and stem-flow.