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July 29-430-Timothy Randhir

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2019 SWCS International Annual Conference
July 28-31, 2019
Pittsburgh, Pennsylvania

Published in: Environment
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July 29-430-Timothy Randhir

  1. 1. FOREST COVER AND WATER QUALITY IN TROPICAL AGRICULTURAL WATERSHEDS Kaline de Mello, Roberta A. Valente, Carlos A. Vettorazzi, and Timothy Randhir University of São Paulo, Brazil University of Massachusetts, Amherst, USA
  2. 2. Introductio n Replacing forest with other land uses can have severe impacts on river water quality, altering its physical, chemical and biological characteristics. FOREST OTHER LAND USE
  3. 3. Introduction Tropical forests are under continual threat due to deforestation and forest fragmentation processes Brazil - the highest rate of annual deforestation in the world – agricultural and pasture expansion Tropical Forest Deforestation
  4. 4. To evaluate the relationship between forest cover and water quality of tropical agricultural watershed in different scales. • Ecosystem services • Landscape planning • Forest conservation and restoration • Watershed management Objectives
  5. 5. • Sarapuí River Basin – São Paulo St, Brazil • 6 experimental small watersheds with different percentage of forest cover 3 forested (≥55%) – S1, S2,and S5 3 degraded (≤35%) – S3, S4, and S6 • Atlantic Forest • Agriculture, Eucapyptus, Pasture and Urbanization Mostly annual crops Study Area
  6. 6. 24 samples October 2013 to October 2014 Temperature (°C) pH Dissolved oxygen (mg.L-1) Streamflow Water samples Water quality and streamflow during a year Turbidity (NTU) IN-SITU WATER QUALITY DETECTOR TURBIDIMETER CURRENT- METER
  7. 7. Water quality analysis Total Nitrogen (mg.L-1) – Kjeldahl digestion Total Phosphorus (µg.L-1) – Spectrophotometric Total Coliforms (NMP) Fecal Coliforms (NMP) Total suspended solids (mg.L-1) Inorganic suspended solids Organic suspended solids GRAVIMETRIC MULTIPLE-TUBE
  8. 8. Analysis Comparing Forested and Degraded Watersheds Statistical analysis • Spatial variation of water quality • Pearson correlation between water quality variables • Linear regression between water quality and stream flow • MANOVA – Hotelling-Lawley • PCA
  9. 9. • Forested watersheds – better water quality (Hotelling-Lawley´s λ = 0.47; F = 5; P = 0.0003) • S4 – High values and temporal variation agricultural area • S5 – good water quality forest • S3 – lowest DO urbanization Forested vs Degraded Results Water quality Streamflow Solids (NTU and SS) Nutrients (TP)
  10. 10. Riparian Analysis Comparing Watershed and Riparian Zone
  11. 11. Water quality variable T Land Use Q • Watershed • Month Mixed models Land use watershed Riparian Zone RDA Global influence on Water quality Watershed vs Riparian Zone
  12. 12. • Forest – good water quality in all models • Pasture – different impacts, in general do not impact water quality negatively • Agriculture and urbanization water quality degradation DO Solids Nutrients Coliforms Forest Urbanization and Pasture DO Urbanization & Agriculture Sólids Nutrients Coliforms Temperature and organic material Drainage of agricultural areas and sewage Watershed vs Riparian Zone Results
  13. 13. Variable Escale R2 Int. Q T Agriculture Pasture Urban DO Watershed 0,72 8,64** 2,46* -0,13** 1,24* -2,41* TSS Watershed 0,60 0,79** 15.21** 1,69** 6,42** OSS Riparian Zone 0,51 0,55** 9,69** 1,75** 2,46* TN Riparian Zone 0,49 4,43** -0,06* -0,09** 5,67** TP Watershed 0,67 3,03** 5,67** 1,64** 4,86** FC Watershed 0,65 2,26** 4,91** 5,04* Mixed models. Watershed vs Riparian Zone Results
  14. 14. Watershed Riparian Zone 82% 75% Pollution gradient Riparian Zone = 30m: Brazilian law... Is that enouth? Watershed vs Riparian Zone Results RDA
  15. 15. Third Analysis Modelling impacts of riparian restoration on water quality SWAT model Sarapuí River Basin
  16. 16. Soil Slope Land use River network Temperature Preciptation Humidity Solar radiation Wind speed Streamflow, sediment and nutrients 2 gates + experimental watersheds Source: Projet, IBGE, CPLA, INMET e ANA Modelling water quality SWAT model
  17. 17. Modelling water quality Model calibration – SWAT-CUP • Streamflow: Daily, Monthly and Yearly - 33 years, 3 warming up • Performance criteria: R², NS, & PBIAS • R², NS, & PBIAS Sensitivity analysis Validation Streamfl ow Sedim ent Nutrien ts
  18. 18. • Better results for monthly streamflow • Performance criteria: R², NS, & PBIAS - good and acceptable values Modelling water quality Results Calibration
  19. 19. Great values of sediment and nutrients at the headwaters Greater slopes and agricultural areas Exception for forested watersheds Figura 9: Distribuição espacial da qualidade da água. Agriculture and urban Rainy season Florest and Pasture Dry season P SS Modelling water quality Results Land use and water quality
  20. 20. Modeling water quality Results Riparian restoration • forest 14% • agriculture 8% and pasture 10% • SS 9,26% • N 22,6% • P 7,89% 30m of Permanent Protected Area
  21. 21. Conclusions • Importance of forest cover in agricultural watersheds; • Agriculture and Urbanization generate more pollutants; • Exposed soil - erosion and runoff - sediments carry pollutants; • Residential areas, even small ones, generate pollution (without sewage collection); • grasslands contribute to water quality; • Water quality parameters respond differently to scales; • Watershed management more important than just riparian conservation; • Riparian restoration as a priority action.
  22. 22. Conclusions • Landscape planning; • Best agricultural practices; • Sewage collection, septic tank; • Forest conservation and restoration; • Holistic view of the watershed and ecosystems in decision making. What to do?
  23. 23. Thank you! • Contact: • Randhir@umass.edu • (413)5453969 • https://eco.umass.edu/people/faculty/randhir-timothy-o/

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