4. Impact of Human Activities on Water Status
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4. Impact of human activities on water status 4.1 Groundwater This section examines the environmental effects 4.1.2 Groundwater chemical status that are apparent in aquifer 8 as a result of the en- vironmental pressures described in Section 3.4.1. In order to be able to closely assess the chemi- The subdivision of aquifer 8 into groundwater cal status of the groundwater in the individual bodies 8-1 to 8-6 has been dealt with in Section groundwater bodies the following three ground- 1.7.2. This subdivision was made on the basis of water chemistry parameters have been exam- the same chemical substances as are examined ined: here. • 2,6-dichlorbenzamid (BAM) • Nitrate 4.1.1 Abstraction of groundwater • Conductivity. Based on large series of soundings, attempts have The method chosen is that recommended been made to identify changes in the groundwa- and described in the Guidance Document on ter potential caused by human activities. Useful groundwater (GD2.8), with the groundwater data are hard to come by as soundings have usu- chemical status being described on the basis of ally been made in the waterworks abstraction the arithmetic mean of the content in the indi- wells. This can lead to pronounced local lower- vidual groundwater bodies together with the ing of the water table, which is not representative respective confi dence intervals. The status for of changes in the general water table. Moreover, 2,6-dichlorbenzamid, nitrate and conductivity there are problems with determining the refer- is shown in Table 4.1.1. The arithmetic mean ence level by the sounding such that systematic and CL(AM) is shown for each component in errors arise. groundwater body 8-1 to 8-6. CL(AM) is the sum Changes in water level have been detected in of the arithmetic mean and the 95% confi dence some wells. These changes can be attributed to interval. Assuming that the data are normally variation in the climate, including the precipi- distributed, 95% of the measured values will thus tation. In connection with the present work it lie below the CL(AM). has not been possible to identify changes in the The data for BAM show that subdivision of groundwater potential that are attributable to aquifer 8 into several groundwater bodies was human activities. Neither has it been possible to the right thing to do in that the average concen- identify an increasing water table despite the fact tration in groundwater body 8-3 is considerably that groundwater abstraction by waterworks has higher than in the other groundwater bodies. If decreased by 30% over the past 10 years, the whole aquifer had been considered to be a 2,6-dichlorbenzamide Nitrate Conductivity Table 4.1.1 (µg/l) (mg/l) (µS/cm) Groundwater status with respect to 2,6- Groundwater body Arithmetic mean CL( ) Arithmetic mean CL( ) Arithmetic mean CL( ) AM AM AM dichlorbenzamid, ni- 8-1 No data 78.5 1 650 trate and conductivity for each of the ground- 8-2 0.02 0.04 5.85 11.73 752.07 823.17 water bodies of aquifer 8. Both the mean and 8-3 0.68 1.83 1.54 3.4 756.55 1 149.08 the CL(AM) (mean + 95% confi dence inter- 8-4 0.04 0.08 8.89 14.55 610.53 667.95 val) are given. 8-5 0.01 0.01 0.32 0.47 697.76 760.53 8-6 0.02 0.04 9.79 24.22 692.79 774.29 Odense PRB Odense Pilot River Basin 97 4.1 Groundwater single groundwater body this would have been detected in groundwater body 8-5, and it has masked, and the BAM concentration would have not been analysed for in groundwater body 8- been high for the whole aquifer. The same applies 1. 2,6-dichlorbenzamid has been detected in an for nitrate, where the concentration is higher in aquifer beneath groundwater body 8-1, though. groundwater bodies 8-2, 8-4 and 8-6 than in the It is therefore concluded that despite the fact that other groundwater bodies. With conductivity, groundwater body 8-1 has not been analysed for only groundwater bodies 8-1 and 8-3 differ from 2,6-dichlorbenzamid, it does not meet the objec- the remaining bodies in aquifer 8. tive for this substance. It transpires that the groundwater bodies The extent of 2,6-dichlorbenzamid contamina- that have been identifi ed on the basis of a raised tion is expected to increase in future as the sub- conductivity (Table 1.7.10) also do have a higher surface groundwater gradually moves deeper. It conductivity (Table 4.1.1). The same applies for is thus expected that the groundwater bodies will BAM and especially for nitrate. Based on the not be able to meet the objectives with respect to groundwater chemical status of the individual pesticides and their metabolites in 2015. Neither groundwater bodies it can be concluded that the is it expected that it will be possible to meet this description of status is in agreement with the sub- environmental objective with the technological division of aquifer 8 into groundwater bodies. solutions currently available. In view of land use and the natural protection above the groundwa- Chemical stratifi cation of the groundwater ter bodies, moreover, it is concluded that ground- bodies water body 8-5 will not become contaminated From the available chemical data it is not possi- with 2,6-dichlorbenzamid. ble to identify any chemical stratifi cation of the groundwater bodies. The reason for this is partly the relatively fl imsy data material, and partly that the groundwater bodies are restricted with respect to their vertical distribution. 4.2 Watercourses Trend in groundwater chemical status Based on the nitrate data, attempts have been 4.2.1 Physical pressures made to identify any trend in groundwater chem- ical status. It has not been possible to identify any Anthropogenic pressure on the watercourses trend, again due to the fl imsy data material, in- in Fyn County really started around 5 000 cluding the lack of large unbroken time series. years ago with the clearing of the woodland for agricultural use, thereby rendering many of the watercourses unshaded. Moreover, from around the 13th Century some of the watercourses were 4.1.3 Objective compliance and risk dammed for mill operation. This – together with of future lack of compliance the establishment of dams for meadow irrigation in the 19th Century – disrupted the continuity The current objectives for the two selected sub- of the watercourses, thereby hindering fi sh such stances, 2,6-dichlorbenzamid and nitrate, are as trout and eel from their natural migration be- described in Section 1.7.3. tween fresh water and sea water. In newer times The characterization of the chemical status other obstructions have arisen too, for example shows that with respect to nitrate, all the ground- culverts under roads. water bodies meet the objective. With groundwa- The appearance of the watercourses has also ter bodies 8-2, 8-4 and especially 8-6, however, been changed through other forms of regulation. there is the future risk that they will not meet the Many naturally meandering or sinuous water- current objective for nitrate (maximum 25 mg/l) courses have been straightened and the beds ex- if the concentration increases. From the existing cavated, and in places the slope has been neutral- data there is presently no evidence to indicate ized by the construction of falls. These activities that the nitrate concentration is increasing in really started in the 18th Century and accelerated these three groundwater bodies, though. up through the 19th Century until the last major As far as concerns 2,6-dichlorbenzamid, the regulation project in 1960, which encompassed a characterization shows that groundwater bod- considerable part of the River Odense (Riis et al., ies 8-2, 8-3, 8-4 and 8-6 do not meet the current 1999). The aim of such regulation was to ensure objectives. No 2,6-dichlorbenzamid has been improved drainage and thereby to increase the Odense 98 PRB Odense Pilot River Basin 4.2 Watercourses possibilities to use the adjoining land for agri- Figure 4.2.1 Relative impact (in cultural production. At the same time, rapid re- N %) of groundwater moval of the water was further ensured in many abstraction on median places through intensive maintenance in the form minimum water fl ow of clearance of all aquatic vegetation as well as in the various catch- vegetation along the banks and borders of the wa- ments within Odense tercourses and dredging of the bed substratum. River Basin. The rela- The regulation, the changed physical condi- tive impact of ground- tions (with soft, unstable bed and rapid drain- water abstraction is ing away of the water), the restricted hydraulic calculated as the total abstraction multiplied interaction with the immediate surroundings by 0.6, which is the (see Section 4.4) and the continued disturbances factor whereby abstrac- contributed – together with pollution – to the tion is expected to af- disappearance of many sensitive plant and animal fect groundwater input species from the watercourses. A few species have to the watercourses. not just disappeared locally, but are no longer Median minimum wa- found in Fyn County at all (see for example Riis ter fl ow is without any et al., 1999). input of wastewater Even though numerous improvements have from treatment plants and is reported as been made to the physical conditions over the “output” from a given past 15 years, including actual restoration and catchment.