Measuring Environmental Impacts of Land Use Changes on Water

Chapter 12

Measuring Environmental Impacts of Land Use Changes on Water Quality with Lysimeters R. Meissner, J. Seeger, and H. Rupp

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UFZ Center for Environmental Research Leipzig-Halle, Department of Soil Sciences, Lysimeter Station, Dorfstrasse 55, D-39615 Falkenberg, Germany

To study and predict environmental impacts of land use changes we operate 200 lysimeters at 6 lysimeter stations. Different types of lysimeters are used to evaluate the effects of intensive and extensive agricultural systems, fallow systems and forestry types on drainage water quality. Lysimeter experiments allow the rapid detection and prediction of the impacts of changes in agricultural management. In particular, they are suitable for studying the transformation and translocation of nutrients and other chemical substances passing through soils and sediments into water systems. The objective of this paper is to discuss a) our different lysimeter set-ups and related experiments, b) the initial results of our lysimeter studies and their impact on land use management and c) the scaling-up of lysimeter data to catchment areas. However, from the point of view of protecting drinking water quality, rotation fallow for one year is not recommended because of the resulting intensified leaching of nitrates. Agriculture in the former East Germany experienced fundamental changes with German unification in 1990. Policies of the European Community (EC) had to be implemented in the five new German states aimed at reducing agricultural overproduction by various means such as extensive cultivation or taking land out of production for several years. As a consequence, 10 % of the 6.2 million hectares of land previously intensively farmed were abruptly left idle. The question was raised, whether or not nutrients and agrochemicals accumulated in the soil during the former intensive cultivation represent a potential risk for the quality of both surface and ground waters. In Germany agriculture is directly responsible for more than 50 % of the nitrogen leached into streams and rivers (1). This pollution takes places primarily

©1998 American Chemical Society

Führ et al.; The Lysimeter Concept ACS Symposium Series; American Chemical Society: Washington, DC, 1998.

163

164 through a diffuse soil - ground and surface water - pathway (2\ Ground water supplies more than 70 % of the drinking water in Germany. Therefore, it is of vital importance to know the quantity and quality of water which leaves the root zone to enter the aquifer and finally the surface water system. Process-oriented lysimeter studies in combination with flow models and verifying field experiments can substantially contribute to knowledge about diffuse pollution and water recharge which is necessary to develop sustainable land management system. Our immediate goal is to establish methods that will allow us to extrapolate lysimeter results to small catchments with similar meteorological and pedological settings.


Description of the Lysimeter Stations and the Experimental Catchment Areas The U F Z Center for Environmental Research operates 6 lysimeter stations at 3 sites in typical regions of the river Elbe catchment, which is the most important one in East Germany (Figure 1). The Continuously Recording Lysimeters at the UFZ Lysimeter Research Station in Falkenberg. The 2 lysimeter stations in Falkenberg represent the Elbe catchment in the northern regions of the federal states of Saxony-Anhalt and Brandenburg. The Station of Large Non-weighable Lysimeters. One hundred and twenty non-weighable lysimeters each with a surface area of 1 m , a total depth of 1.25 m and free drainage were constructed in 1983. The lysimeters were filled with disturbed soil profiles (sandy loam, sand, loam, loess) commonly found in the catchment area of the Elbe river and the northern part of East Germany. Between 1985 and 1990 a complex experiment was implemented to develop systems that optimize water management and agricultural production in protected water catchments by minimizing the translocation of relevant macronutrients (Ν, Ρ, K ) from the root zone at high crop yields (3). The soils in the lysimeters were intensively fertilized and irrigated during summer according to common cultivation practices in the former GDR (East Germany). After the reunification of Germany the experiments were adapted to investigate the impacts of changes in agricultural land management (mainly extensification and leaving land fallow) on the water and solute balance. In 1995 four additional non-weighable lysimeters with a surface area of 1.0 m and a total depth of 1.75 m with free drainage and a system for regulating the water table were constructed. These lysimeters were filled with representative soils and sediments from open-pit brown coal mining near Leipzig. The objective is to measure the ground water recharge in these mining landscapes and to determine the influence of rising ground water tables on the water and solute balance. The drainage water from each lysimeter is collected in a separate storage container. At least once a month, the volume of water leached is measured and samples analyzed chemically. 2

2



165

Figure 1. Catchment area of the Elbe river and geographical location of the U F Z managed lysimeter stations and the experimental catchments.


166 The Station of Small Non-weighable Lysimeters. Twenty non-weighable lysimeters with a surface area of 0.20 m , different depths of 0.25 m, 0.5 m, 1.0 m, 2.0 m, 3.0 m and free drainage were filled with sandy and loamy soil profiles in 1989. In November 1995 an experiment was set up to investigate the behavior of different tracers (Cl, Br, D20, N) in soils (4) and the leaching of hazardous organic substances (e.g. hexachlorocyclohexane, methoxychlor) commonly found in riverside areas of the former East German chemical industry. The lysimeters were closed on top to exclude plant growth and plant uptake as well as evaporation. Precipitation is simulated by irrigation. The drainage water from each lysimeter is collected in a separate storage container. At least once a month, the volume of water leached is measured and samples analyzed chemically. 2


15

The Lysimeter Stations in Colbitz. There are 2 lysimeter stations in the village of Colbitz representing a forest and a heathland commonly found in the middle of East Germany. The Non-weighable Lysimeter Station. One non-weighable lysimeter with a surface area of 660 m , a total depth of 4.0 m and free drainage was filled with a sandy soil from a forested area and planted with pine trees in 1973. The main objective of this experiment is to quantify the influence of atmospheric deposition and different types of forestry management on the water and solute balance (5). Three times a month the volume of drainage water is measured and samples are taken for chemical analysis. 2

The Weighable Lysimeter Station. The 12 monolithic and weighable lysimeters with a surface area of 1.0 m , a total depth of 2.0 m and free drainage were filled with heathland soil profiles of the area and planted with different types of heathland vegetation in 1968. The main objective of this experiment is to quantify the influence of different heathland management systems on the water and solute balance (6). The amount of drainage water and the évapotranspiration is measured daily. At least once a month a sample is taken from each container for chemical analysis. 2

The Lysimeter Station in Brandis. The 2 lysimeter stations in the village of Brandis near the city of Leipzig represent the area of low precipitation (< 500 mm annually) in middle Germany. The Weighable Lysimeter Station. The 24 monolithic and weighable lysimeters have a surface area of 1.0 m , a total depth of 3.0 m and free drainage. Twenty-one monoliths represent agricultural soil profiles of the area. Three monoliths were sampled from an open-pit brown coal mining area near Leipzig. 2


167 The Non-weighable Lysimeter Station. The 19 monolithic and nonweighable lysimeters with a surface area of 1.0 m , a total depth of 2.0 to 2.2 m and free drainage were filled with representative agricultural soil profiles of the region. The lysimeter experiments of both stations were set up in 1980 to investigate the influence of agricultural management practices and ecological forms of land use (extensification - without application of fertilizer) on the water balance, the leaching of nutrients and heavy metals, and the production of trace gases (7). Every day the amount of drainage water and the évapotranspiration (for the weighable lysimeters only) is measured. At least once a month a sample from each lysimeter is taken for chemical analysis. Downloaded by PURDUE UNIV on July 8, 2016 | http://pubs.acs.org Publication Date: September 10, 1998 | doi: 10.1021/bk-1998-0699.ch012

2

Experimental Catchment Areas. A l l lysimeter experiments are linked to representative experimental catchment areas in the field to establish and verify extrapolation domains. The "Schaugraben" Catchment. Lysimeter experiments in Falkenberg are mainly linked to the "Schaugraben" catchment (about 2,500 ha). The "Schaugraben" is a tributary of the river Elbe in north-east Germany. The "Schaugraben" lowland provides a good example of the change from former socialist co-operative to private farming. The "Droemling" Catchment. The lysimeter station in Colbitz is linked to the Colbitz-Letzlinger heathland within the "Droemling" catchment (about 55,000 ha) which is the main ground water recharge area for the water supply of Magdeburg, the capital of Saxony-Anhalt. The "Parthe" Catchment The lysimeter station in Brandis is located in the "Parthe" catchment (about 36,000 ha) near Leipzig which is mainly urban. Results of Lysimeter Experiments and Scaling-up From the various lysimeter experiments the results of the one on effects of land use change on drainage water quality in the "Schaugraben" catchment can be taken as an example. For this experiment 30 lysimeters filled with sandy loam and previously cultivated intensively are treated in 2 replications as follows: -10 lysimeters with a permanent fallow (beginning on August 1, 1991); - 10 lysimeters with a rotation fallow for one year (the first fallow period was implemented from August 1, 1991 to July 31, 1992) before resuming intensive crop cultivation; - 10 lysimeters are treated according to B M P (best management practices, whereby fertilization and irrigation is performed in accordance with plant requirements for nutrients and water and with ecological and economical demands).



168

The lysimeter experiments showed that introducing a long- term fallow (five years) or a rotation fallow for one year to a continuously intensively farmed land results in measurable changes in the water and solute balance within a short time (8). In the fallow treatments deep percolation increases and plant nutrient uptake decreases. Hence, in the first year of fallow the leaching of cations and anions increases compared to intensively cropped plots (Figure 2 a). Leaching of calcium, magnesium and potassium is reduced in the second year (Figure 2 b). In the third year, deep percolation and cation leaching increased in all plots irrespective of cultivation and fertilization practices because the precipitation was 53 % more than average (Figure 2 c). Because of the former intensive cultivation the base saturation of the soils is obviously sufficient to release considerable amounts of cations with increasing volumes of drainage water. In the fourth year, the long-fallow showed slightly, but not significantly, more deep percolation but with reduced leaching of cations and anions (Figure 2 d). No significant changes in the leaching of phosphorus were detected in fallow treatments because of its firm bonding with soil colloids are unlikely, at least not in the short run. Water bodies are faced with a latent risk of phosphorus accumulation, particularly in areas with sandy soils where mineral and organic fertilizers such as liquid manure, sewage sludge and composted bio-wastes are applied (9). Leaching of chloride and sulfate became significantly less in the long-term fallow treatment from the second year onward irrespective of changes in deep percolation. Without fertilization or irrigation, the soils are insignificant sources for leaching chloride and sulfate. Anion leaching increases highly when intensive cultivation resumes after the rotation fallow. No significant difference was detected among the treatments with respect to nitrate. Cumulative nitrate leaching for the four-year monitoring period was highest in the rotation fallow. Compared with lysimeters treated according to B M P , nitrate leaching in the year of set aside was increased by approximately 55 % and in the year of resuming intensive agricultural production by 30 %. Application Catchment

of Lysimeter Results to the

Experimental

"Schaugraben"

In order to predict the effects of land use changes on N-losses from the soil and N loads of the stream for the catchment area of the "Schaugraben" we applied and verified the results of the lysimeter experiments in the field. The field experiment concerns the "Schaugraben" catchment, which is about 15 km away from the lysimeter station at Falkenberg (Figure 3), has loamy soils and similar meteorological conditions. Agriculture (61 % arable land; 21.5 % pasture) is the main land use in the catchment. At the headwaters 15.3 % of the area is covered with forest. Historic and recent land use patterns (i.e., forest, pasture, and cropped land including various types of crops and fertilizer regimes) in the "Schaugraben" catchment have been recorded since 1990 and mapped in a GIS. The catchment area was subdivided into 4 sections (subcatchments). Four gauging stations were set up and discharge and water



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170

Figure 3. Experimental catchment "Schaugraben" with its subcatchments and land use patterns.



171 quality have been measured every two weeks since October 1992. In 1996 two sets of ground water wells were installed to determine the flow and quality of ground water. At the outlet of the "Schaugraben" stream (subcatchment 4) discharge and water quality has been monitored automatically since May 1997. To extrapolate the results of the lysimeter experiments, the amount of seepage water measured in the lysimeters has to match the ground water recharge in the catchment which was a) calculated according to equations commonly used in Germany and b) the discharge measured in the field (in the northern region of East Germany the ground water recharge is about equivalent to the discharge, to which surface water contributes very little) (10). The more accurate the estimate of ground water recharge, the better is the assessment of the leaching of nutrients from the unsaturated zone. The quantities of drainage water determined in the long-time lysimeter studies fell within the range of the calculated mean annual ground water recharge rates (Table I)-

T A B L E I. Comparison of results from long-time lysimeter studies with calculated mean annual ground water recharge in the "Schaugraben" catchment Reference Arable land** Pasture** Forest** Σ Ground water recharge** (23.80 km ) (14.83 kml) (5.23km ) (3.74km ) 2

Calculated recharge Model "RASTER" (11) Bagrov-Glugla* (12) Renger-Wessolek (13) Doerhoefer-Josopait (14) Long-time lysimeter studies

2

2

-

-

-

95 87 96

-1 15 16

-1 11 11

125 93 113 123

72

23

2

97

*Long- term mean precipitation at the Falkenberg lysimeter station: 504 mm Long- term mean evaporation rate at the Falkenberg lysimeter station: 565 mm ** Ground water recharge in mm Comparing the amount of drainage water measured in the lysimeters and the discharge measured by the State Environmental Protection Agency in Magdeburg in this region during 1993 and 1994 revealed a better match than results of mean annual ground water recharge models commonly used for water management in Germany (Table Π). Being located in the region our lysimeters are exposed to the same meteorological conditions while long-time ground water recharge models are not sensitive to shortterm variations of meteorological parameters.


172 The drainage water quantities determined with the lysimeters fall within the variation of ground water recharge rates calculated according to equations commonly used in hydrology. They also comparable to the discharge measured in the field. Therefore, we assume that leaching of nutrients measured with the lysimeters reflects the conditions in the catchment area with sufficient accuracy for extrapolation.

Table Π. Comparison of ground water recharge rates in lysimeters and measured discharges in the "Schaugraben" catchment Measured discharge

Lysimeter data Downloaded by PURDUE UNIV on July 8, 2016 | http://pubs.acs.org Publication Date: September 10, 1998 | doi: 10.1021/bk-1998-0699.ch012

1993 Subcatchment 1

42 mm

55 mm

Subcatchment 2

62 mm

77 mm

Subcatchment 3

63 mm

71 mm

Subcatchment 4

70 mm

85 mm 1994

Subcatchment 1

261 mm

343 mm

Subcatchment 2

284 mm

298 mm

Subcatchment 3

285 mm

367 mm

Subcatchment 4

310 mm

422 mm

Determination of N-loss from the Soil. The type of land use is an important consideration when attempting to quantify and predict nitrate leaching and has been surveyed in the experimental catchment every year since 1990 (Table ΙΠ). Table ΙΠ. Cropping systems (% of arable land) in the "Schaugraben" catchment between 1990 and 1995 Beginning of Current land use land use change in 1990 in 1995 55 Cereals, rape seed 52 16 Corn 7 6 Potatoes 15 8 Sugar beets 9 11 One year rotation fallow 4 4 Other plants 13


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Based on annual results of the lysimeter studies (N leached in drainage water) and the actual land use in the catchment (crops planted, fallow, pasture, forest) an estimation of N-loss from the soil was made for each year (Table IV).


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Table TV. Estimated N-loss of the "Schaugraben catchment based on lysimeter data for the year 1993 N-loss "Schaugraben" catchment Lysimeter experiments Land use Area Seepage water N-concentration N-leaching from the soil ha kg/ha mm mg/l kg Cereal 31,140 1,038 30 65 46 Corn 149 5,215 71 35 49 6,372 Potatoes 118 54 132 41 1,680 Sugar beets 60 28 82 34 7,080 60 Rotation fallow 118 80 75 6,276 Pasture 523 12 55 22 Forest 0 372 0 0 0 57,763 Σ Determination of N-load of the Stream. Based on the discharge measured at 4 gauging stations and analysis of its N-content, the annual N-load was calculated for the whole "Schaugraben" catchment and each subcatchment since 1993 (Table V). 44

Table V . Calculated N-load of the "Schaugraben stream based on measured data for the year 1993 N-load Mean Measured discharge N-concentration from the stream mg/l Tm kg 4,500 Gauging station 1 30 149 14,127 14 Gauging station 2 1,002 18,416 Gauging station 3 12 1,538 26,612 Gauging station 4 2,236 12 3

Comparison between N-loss from the Soil and N-load of the Stream. The N loss from the soil and N-load of the stream at the bottom of the catchment reveal a difference of 30,721 kg/year Ν and 32,993 kg/year Ν for the hydrological cycle November to October in 1993 and 1995, respectively (Figure 4). The most important reason for these differences is probably the highly variable hydrological regime. At present the whereabouts of these amounts of Ν



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Measuring Environmental Impacts of Land Use Changes on Water

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