(4) Modelling:

The Soil Water Assessment Tool (SWAT) (Arnold et al. 1998) is a river basin scale and process orientated ecohydrological model under public domain. It is applied widely for meso-scale ecohydrological modelling on all continents and in different ecosystems (Gassman et al. 2007). The major goal of the development of SWAT was to quantify management practices and scenario analysis in complex watersheds. It is a continuous time routing model what operates with a daily time step for 1-100 years. The model is coded in FORTRAN 90 and the update version SWAT 2005 can be run in an ArcGIS, ArcView-GIS and MapWindow-GIS environment, too.

SWAT contains process descriptions for:

Hydrology (based on water balance equation):Precipitation (spatial and temporal), runoff generation, evapotranspiration, interception, infiltration

and percolation, soil water balance, groundwater recharge; Nutrients and chemicals:

Nitrogen, phosphorus cycling, pesticides and bacteria (mineralization, nitrification, denitrification, leaching, fertilisation, pesticide dynamics);

Erosion (based on MUSLE) and sediment transport:Sediment detachment, sediment transport and routing, sediment deposition;

Channel processes:Channel routing, sediment routing, chemical routing;

Plant growth and agriculture:Growth cycle, biomass production and management practices (crop rotations, tillage, biomixing,

grazing, irrigation, water impoundment)

Model application and scenario development concerning land use change, climate change and agricultural production of different crops and management practices to

assess: a.) interactions of availability of water and nutrient resources, erosion and

their cycling with intensive biomass production; b.) impacts of sustainable management options such as crop and plant rotation

schemes on water, sediment and nutrient cycling; c.) biomass production as a function of different crops and agricultural practices considering

different schemes to minimise soil erosion and nutrient depletion

(1) Introduction and research question:

Brazil’s natural ecosystems of the state Mato Grosso included Cerrado, Pantanal and rainforest. Between 1992 and 2005 extensive forest clearance rates of 5000 to 11.000 km² and 2000 to 4500 km² per year from 2006 has been ascertained for mechanised agriculture in Mato Grosso . The soy production has increased in the same period from 3 to nearly 20 Million tons per year (see Figure 4) and further expand can be easily implemented in the Cerrado and forest transition region (Jasinski et al. 2005). This development is enhanced by the paving of highways (Cuiaba-Santarem) as export corridor for cash crops using the Amazon River then (Fearnside 2007).

To produce this high biomass yields it is required to applicate large amounts of fertilizer and lime because the dominating dystrophic soil type Oxisol shows an acidic reaction which reduces the P availability (Wilcke & Lilienfein 2005).

The interactions between current land-use such as continuous crop production under intensive management and the biogeochemical and hydrological cycling have to this end not received much attention. We want to use a meso-scale ecohydrological modelling tool (SWAT) to simulate current and future feedback mechanisms. To enable modelling, we plan an extensive field campaign that focuses on the two key interacting compartments to further understanding vegetation-soil-water interactions.

(2) Study Area

The Tenente Amaral catchment is situated in the Northeast of the Pantanal Basin with an extension of nearly 865 km² and elevation ranging between 400 and 800 m a.s.l.. The climate is Aw (humid tropical savanna climate) according to the Köppen classification with a distinctive dry season between Mai and September. The mean average temperature is about 25 °C with an annual average rainfall of 1400 mm. The Rio Tenente Amaral is a tributary of the São Lourenço River which is a major feeder of the Pantanal floodplain. Erosion is figured out to be a major threat in this catchment which comes along with continuously increasing sediment discharges in the São Lourenço River in the last decades, too (Horowitz and Walling 2005). Wantzen et al. (2006) showed in an impact assessment approach that 90% of the catchment is moderately or strongly impaired. It is believed that the combined effects of land-use change lead to high concentrations of sediment-attached nutrients and has strong impact on water quality and pollution through siltation in the Pantanal. These negative effects can be strengthened if the predicted double cropping practice for soybean will take place in the Cerrado ecosystem (Wantzen et al. 2006).

Ecohydrological modelling of vegetation dynamics and water

and nutrient cycling for meso-scale in heavily modified

agricultural sites in the south of Mato Grosso, BrazilPhilip Hunke and Eva N. Müller

Institute of Earth and Environmental Sciences, University of Potsdam, Postfach 60 15 53

3. Field campaigns

I. Effects of vegetation/land use on water resources (dry period 2010)� Impacts of land use and land use change on aquatic ecosystems� Description of spatial water quality pattern (i.e. stream order, landscape characteristics)

� “Snapshot sampling” (Grayson et al. 1997) of 50 water samples with analysis and measurements on pH, Temperature,

Specific Conductance, Salinity, Dissolved Oxygen, Depth, Turbidity, Redox potential, Alkalinity, Nitrate/Nitrite, Ammonia, Phosphate and Dissolved Organic Carbon

Mato Grosso

2007: 25 Mio ha

SWAT 2005

Hydrology Water quality

Land cover

Water bodiesChannel processesManagement practices

Sediment

Climate

Pantanal

Figure 2: Contrasting of agricultural production and natural forest

Figure 3: Soy monocultures (all Photographs by Frank Bäse) Figure 4: Annual soy production in Mato Grosso (Wantzen et al. 2006)

II. Effects of vegetation/ land use on soil resources � Effects of landscape characteristics on soil properties (dry period 2010)� Effects of cultivation duration (2-20 years) and different management practices on soil (in 2011)

� Sampling sites along a topographical gradient to collect data on soil type texture, soil colour, soil pH, soil aggregate stability and

infiltrability by means of simple field techniques� Sampling on sites of different land use and management practices on Oxisol with additional analysis on Ammonia, Nitrate, P, K,

Mg and SOC

Figure 5: Proposed water and soil sampling locations (for the field campaign from Mai-July 2010)

1. Corrego Brilhante

2. Corrego Tenente Amaral

3. Corrego Verde

4. Corrego Saia Branca

Figure 6: Tenente Amaral catchment

(based on SRTM data)

Figure 1: Original and remaining Cerrado distribution in Brazil (Marris 2005)

Figure 7: Main routines of

the SWAT model

Cerrado:

� second largest of Brazil‘s biomes (original expanse 2 million km²)

� characterised by Oxisols with low nutrient contents

�Aw climate with a dry period of 5 month (May-September)

� mosaic of different vegetations types (tree and scrub savanna grassland, closed

canopy forests, gallery forests)� Biodiversity Hotspot (4500 endemic

species)� past 35 years more than half of the area was taken for agriculture (beef and

soy)� only 2% under protection

�Current deforestation rates mean that the ecosystem is gone by 2030 (Conservation International)

References:

Arnold JG, Srinivasan R, Muttiah RS, Williams JR (1998) Large area hydrologic modelling and assessment part I: Model development. J Am Water Resour Assoc 34(1):73–89

Fearnside, PM. (2007) Brazil's Cuiaba-Santarem (BR-163) Highway: The environmental cost of paving a soybean corridor through the amazon. Environmental Management 39: 601-614.

Gassman, P. W., Reyes, M. R., Green, C. H. & Arnold, J. G. (2007) The Soil and Water Assessment Tool: historical development, applications and future research directions. Trans. Am. Soc. Agric. Biol. Engrs 50(4), 1211–1250.

Grayson, R. B., Gippel, C. J., Finlayson, B. L., & Hart, B. T. (1997). Catchment-wide impacts on water quality: the use of 'snapshot' sampling during stable flow. Journal of Hydrology, 199, 121-134.

Horowitz, A.J., Walling, D.E. (Eds.) (2005) Sediment Budgets 2- Proceedings International Symposiums on Sediment Budgets, Foz du Iguacu. International Association of Hydrological Sciences, no. 292, IAHS Press, Wallingford, UK,

Marris, E. (2005). The forgotten ecosystem. Nature, 437 (October).

Wantzen, K., Siqueira, A., da Cunha, C. & de Sá, M. (2006) Stream-valley systems of the Brazilian Cerrado: impact assessment and conservation scheme. Aquatic Conservation: Marine and Freshwater Ecosystems, 16, 713–732.

Wilcke, W. & Lilienfein, J. (2005) Nutrient leaching in oxisols under native and managed vegetation in Brazil. Soil Science Society of America Journal, 69, 1152

Acknowledgements:Universidade Federal

de Mato Grosso