Gulf Hypoxia and Water Quality in the Upper Mississippi River Basin

Size: px

Start display at page:

Download "Gulf Hypoxia and Water Quality in the Upper Mississippi River Basin"

Maria Sanders
8 years ago
Views:

1 Gulf Hypoxia and Water Quality in the Upper Mississippi River Basin Catherine L. Kling Iowa State University Least Cost Control of Agricultural Nutrient Contributions to the Gulf of Mexico Hypoxic Zone, Sergey Rabotyagov, Todd Campbell, Manoj Jha, Hongli Feng, Philip W. Gassman, Lyubov Kurkalova, Silvia Secchi, and Catherine L. Kling.

2 Overview Water quality related to water quantity, floods, climate, hydrology, and land use, which are all related economics and policy Gulf hypoxia and water quality in UMRB Modeling system for Upper Mississippi River Basin Water quality and hydrology Economics/land use models 2

3 Gulf Hypoxia Over 400 hypoxic areas worldwide, combined affected area of 245,000 km2 (Diaz and Rosenberg, 2008) Naturally occurring, but significantly enhanced by anthropogenic sources of nutrients 43% N and 41 % P reaching hypoxic zone originates from UMRB (USGS) Gulf of Mexico effects still poorly documented, brown shrimp fishery effects, recreational fishing 3

4 2008 Hypoxic Zone 2 nd largest on record, ~ size of New Jersey 4

5 Upper Mississippi River Basin 189,000 square miles in seven states, dominated by agriculture: 67% of total area, > 1200 stream segments and lakes on EPAs impaired waters list, 5

6 How to Address? Enormous number of farm fields/decision makers Each : one or more land use/conservation practices Retire land (e.g., CRP), Reduce tillage, Terraces, Contouring, Grassed Waterways, Reduce fertilizer, better timing, etc. Costs and effectiveness vary across locations Other complications: Biofuels, Climate change Other environmental concerns 6

7 UMRB Modeling System Designed to support policy design and to understand consequences of land use change Components: SWAT model linked with land use economic model, loads of data Evaluation policies by running scenarios Posit changes in prices or policies (taxes, cap and trade, etc.) Predict changes in land use (shift crop choices, implement conservation practices, retire land from production) Evaluate water quality effects of a configuration of conservation practices 7

8 SWAT Physically based and continuous watershed based hydrology and water quality model, daily time step Developed to predict impacts of land management practices on watershed hydrology and water quality Watershed divided into sub watersheds, then HRUs, mass balances performed at HRU level, loadings routed through main channels, reservoirs to the watershed outlet Extensively used world wide; over 250 peer reviewed publications

9 Key Data Sources Land use data: 1997 NRI database, 114,000 survey points in UMRB (non-gis),comprehensive cropping history (rotation),other land use data Topography: 30m DEM, USGS Seamless Data Distribution System, Climate data: Illinois Water Survey, 535 stations across UMRB Fertilizer rates and tillage data, Cropping Practice Survey, ARMS, CTIC Soil data, derived from USDA Soils5 Data Economics cost data, crop budgets, state conservation program costs, land retirement (2007 rental rates)

10 UMRB Watershed Model Sub Basin NRI points Average size NRI point (Acres) HRU Count , , , , , , , , , ,

11 Using Integrated Models to provide information on Gulf Hypoxia 1. Hypoxia Action Plan has a goal of reducing the size of the zone to 5,000 km2 by What would be least costly way to achieve this? Using water quality model, analyze all the feasible scenarios, picking cost-efficient solutions But, if there are N conservation practices possible for adoption on each field and there are F fields, this implies a total of possible N F configurations to compare 30 fields, 2 options over 1 billion possible scenarios Genetic Algorithm provides approximate solution 11

12 One possible watershed configuration a Genetic Algorithm lingo Field = gene Practice options =allele set watershed configuration = individual (described by set of genes) Population = set of configurations a d a b a d b a a a b c 13 Fields 4 conservation practices 4 13 = >67 million possible configurations 12

13 Algorithm flow diagram Individual = watershed configuration = specific assignment of practices to fields Population = set of watershed configurations 13

14 Pareto frontier: UMRB 14

15 Cost, % of baseline Tradeoffs of NPS control costs and water quality benefits Phosphorus loadings at the outlet vs. costs Empirical cost curve for phosphorus reductions Unconstrained cost curve Binding constraint on 30% N reduction P loadings, % of baseline In this case, nitrate reduction constraint is binding up to a 50% reduction in P This suggests an asymmetry in the control of the two nutrients in the UMRB 15

16 Cost, % of baseline Tradeoffs of NPS control costs and water quality benefits Nitrate loadings at the outlet vs. costs Empirical cost curve for nitrate reductions Nitrates, % of baseline Unconstrained cost curve Binding constraint on 30% P reduction Thus, if a policy seeks to reduce N by more than 20%, more than 30% reductions in P follow 16

17 Nitrate-N loading that yields 30% nitrate-n and 36% P loading reduction Annual additional cost: $ 1.4 billionost)

18 USDA payments for farms in Iowa ($million, From EWG) Year Conservation Payments Disaster Payments Commodity Payments Total USDA Payments 2000 $ $15.63 $2, $2, $ $20.26 $1, $1, $ $18.00 $ $ $ $65.30 $ $1, $ $1.30 $1, $1, $ $85.00 $1, $2,

19 Next Steps Compare cost savings to alternative decision rules Look at sensitivity of costs to climate change by incorporating regional climate model predictions into modeling framework Investigate policy design: how do we design incentives to achieve improvements in water quality at low cost? 19

So far the effort, outlined in the state s Nutrient Reduction Strategy to reduce hypoxia in the Gulf, has been voluntary.

So far the effort, outlined in the state s Nutrient Reduction Strategy to reduce hypoxia in the Gulf, has been voluntary. Push is on for Iowa to clean up its water State leaders are counting on farmers to adopt conservation practices to protect waterways, soil By Donnelle Eller, Des Moines Register; Nov. 9, 2013 EAGLE GROVE,