1

Iowa Conservation Practices: Historical Investments, Water

Quality, and Gaps

(Final progress report)

February, 2007

(revised version)

October, 2007

3

Project OverviewProject Overview GoalsGoals1.1. What conservation practices are What conservation practices are

currently in place in Iowa, what is currently in place in Iowa, what is their coverage, and what is the cost their coverage, and what is the cost of these practices? of these practices?

2.2. What are (and have been) the effects What are (and have been) the effects of this investment on water quality? of this investment on water quality?

3.3. What would it take to improve water What would it take to improve water quality to obtain specific standards?quality to obtain specific standards?

5

Surveys UsedSurveys Used

NRINRI CTICCTICDescriptionDescription USDA SurveyUSDA Survey Reported findings from the USDA’s Crop Reported findings from the USDA’s Crop

Residue Management SurveyResidue Management Survey

CoverageCoverage Contour FarmingContour FarmingContour StripcroppingContour StripcroppingFilter StripsFilter StripsGrassed WaterwaysGrassed WaterwaysTerracesTerracesErodibility MeasuresErodibility Measures

CRPCRPTillage PracticesTillage Practices

YearsYears 19971997 20042004

Nature of SurveyNature of Survey statistically based survey.statistically based survey.Data were collected using a variety of imagery, Data were collected using a variety of imagery, field office records, historical records and data, field office records, historical records and data, ancillary materials, and a limited number of on-ancillary materials, and a limited number of on-site visitssite visits

““best estimates” of district conservationist are best estimates” of district conservationist are combined with Cropland Transect Surveys combined with Cropland Transect Surveys

PositivesPositives 1. Records the total coverage of the practices 1. Records the total coverage of the practices (both those that received financial assistance (both those that received financial assistance and those that were installed voluntarily without and those that were installed voluntarily without funding).funding).

1. Records the total coverage of the practices 1. Records the total coverage of the practices (both those that received financial assistance (both those that received financial assistance and those that were installed voluntarily and those that were installed voluntarily without funding).without funding).

NegativesNegatives 1. Conservation practice usage is calculated 1. Conservation practice usage is calculated from a sample and so assumptions are made from a sample and so assumptions are made about the population.about the population.

1. Aggregate data (at the county level) that 1. Aggregate data (at the county level) that cannot be directly used in water quality cannot be directly used in water quality modeling.modeling.

6

Statewide average costStatewide average cost

Practice Statewide Average Cost

Grass Waterway $2,127/acre

Terrace $3.57/ft

Water & Sediment Control Basin $3,989/structure

Grade Stabilization Structure $15,018/structure

Filter Strip $116.83/acre

Contour Buffer Strip $78/acre

Riparian Forest Buffer $486/acre

Wetland Restoration $245/acre

Nutrient Management $4.09/acre

Contour Farming $6/acre

No Till $17.94/acre

Continuous CRP $142/acre

General CRP $97/acre

7

Statewide CoverageStatewide Coverage

Practice Statewide Coverage

Grass Waterway (NRI) 2,225,900 acres

Terrace (NRI) 1,997,900 acres

Contour Stripcropping (NRI) 236,800 acres

Contour Farming (NRI) 5,148,200 acres

Mulch Till (CTIC) 8,290,000 acres

No Till (CTIC) 5,220,000 acres

CRP (CRP program) 1,894,488.2 acres

8

Total Costs of the PracticesTotal Costs of the PracticesPracticePractice CostCost

TerracesTerraces$692,147,6$692,147,6

7676

Grassed Grassed WaterwaysWaterways

$95,090,42$95,090,4244

Contour FarmingContour Farming$30,889,20$30,889,20

00

Contour Contour StripcroppingStripcropping $3,552,000$3,552,000

No-TillNo-Till$104,308,7$104,308,7

4040

Much TillMuch Till$82,861,90$82,861,90

00

CRPCRP$175,878,3$175,878,3

6565

$37,194,949

$397,490,205

The first two practices are structural practices.

Divide the installation costs over the lifespan of the practices (terrace: 25yrs, GW: 10 yrs), then the sum of annual payment is: $37,194,949.

The cost numbers for the rest of the practices are annual payments.

Then the total annual costs would be:

$37.2million + $397.5million = $434.7

10

13 Iowa Watersheds13 Iowa Watersheds

11

% Improvement due to Existing % Improvement due to Existing PracticesPractices

  Flow Nitrate Org N Min P Org P Total N Total P

Boyer -8 23 56 45 50 38 48

Des Moines -8 14 39 29 37 15 33

Floyd -4 19 42 41 44 25 42

Iowa -5 10 41 0 40 13 25

Little Sioux -7 20 52 40 50 24 47

Maquoketa -1 8 42 37 42 17 39

Monona -3 15 49 54 61 26 58

Nishnabotna -3 21 52 45 47 33 46

Nodaway -2 28 56 49 51 37 50

Skunk -6 14 46 40 44 21 42

Turkey -5 5 38 30 37 18 34

Upper Iowa -3 7 48 38 47 18 45

Wapsipinicon -8 6 46 34 45 11 40

13

What would it take to What would it take to improve improve

water quality?water quality? Numerous conservation practices Numerous conservation practices

could be implemented on any field, could be implemented on any field, each with different levels of each with different levels of effectiveness and costseffectiveness and costs

Solving for the least-cost solution Solving for the least-cost solution requires comparison among a very requires comparison among a very large number of possible land use large number of possible land use scenariosscenarios

15

ApproachApproach

Evolutionary algorithms provide one Evolutionary algorithms provide one search strategysearch strategy

mimic the power of evolution, which, mimic the power of evolution, which, in effect, is a method of searching for in effect, is a method of searching for solutions among an enormous amount solutions among an enormous amount of possibilities (Mitchell, 1999)of possibilities (Mitchell, 1999)

Outline basic idea onlyOutline basic idea only

16

Pareto OptimalityPareto Optimality Point A is not clearly Point A is not clearly

preferred to point B preferred to point B (since B has lower (since B has lower costs, but higher costs, but higher pollution)pollution)

Point C ought to be Point C ought to be preferred to point D preferred to point D (since D exhibits both (since D exhibits both lower costs and lower lower costs and lower pollution levels)pollution levels)

We try to identify a We try to identify a frontier like ABC and frontier like ABC and then push it toward the then push it toward the originorigin

18

Flow diagramFlow diagram

20

Land use options Land use options consideredconsidered

1. Land Retirement

2. Corn-Soybeans, Conventional Tillage

3. Corn-Soybeans, No-Till

4. Corn-Soybeans, 20% Fertilizer Reduction

5. Contouring

6. Terracing

7. Combinations (as sensible) of above practices

23

State-wide resultsState-wide results Apply the evolutionary algorithm to the 13 Apply the evolutionary algorithm to the 13

watershedswatersheds A challenging task, given the number of HRUs and A challenging task, given the number of HRUs and

current computing capacitycurrent computing capacity Results presented are based on over 91 days of CPU timeResults presented are based on over 91 days of CPU time Over 116,000 SWAT model runsOver 116,000 SWAT model runs

Overall, the algorithm is able to identify scenarios Overall, the algorithm is able to identify scenarios which result in significant reductions in loadings which result in significant reductions in loadings of nitrates and phosphorus relative to baselineof nitrates and phosphorus relative to baseline

Results must be interpreted with caution: Results must be interpreted with caution: it is possible that better solutions could be identified, it is possible that better solutions could be identified,

given enough CPU timegiven enough CPU time

30

State-wide results: P-N State-wide results: P-N targetingtargeting

WatershedP loading,

kg

Actual P loading, % of baseline

P concentration, mg/L Gross Cost, $ Net cost, $

N loadings, in % of baseline

N concentration, mg/L

Boyer 648,398 59.7 0.742 14,950,585 4,708,885 66.2 2.232

Des Moines 1,482,270 58.387 0.129 190,010,000 145,910,600 75.9048 4.514

Floyd 295,676 52.2 0.560 8,056,582 2,778,832 64.2 4.494

Iowa 2,432,160 67.1 0.206 193,575,632 109,999,532 75.2 6.189

Little Sioux 800,924 57.5 0.491 33,142,350 11,949,650 64.2 3.617

Maquoketa 14,589 39.8 0.323 2,218,699 -15,780,401 60.6 3.682

Monona 200,116 60.3 0.546 7,753,342 -1,491,738 55.1 4.158

Nishnabotna 2,068,920 67.3 0.625 43,579,662 13,676,562 65.1 2.408

Nodaway 354,088 61.6 0.401 8,140,247 3,370,077 72.9 2.049

Skunk 1,842,720 63.6 0.482 50,379,561 29,196,661 75.2 2.595

Turkey 981,900 71.3 0.381 17,057,490 1,707,090 74 2.999

Upper Iowa 130,640 60.5 0.100 11,038,459 3,740,489 75.8 1.635

Wapsipinicon 413,100 67.6 0.135 33,030,359 12,112,059 70 3.861

31

State-wide summary of P-N State-wide summary of P-N targetingtargeting

The total gross cost of implementing the The total gross cost of implementing the management scenarios is almost $613 million management scenarios is almost $613 million a year a year

The net cost is estimated to run just under The net cost is estimated to run just under $322 million a year$322 million a year

Following the prescriptions of the algorithm Following the prescriptions of the algorithm for each of the watersheds results in the state-for each of the watersheds results in the state-wide reduction in phosphorus loadings of over wide reduction in phosphorus loadings of over 36%36%

would simultaneously result in the state-wide would simultaneously result in the state-wide reduction in nitrate loadings of over 31%reduction in nitrate loadings of over 31%

33

Comparison of Comparison of selected watersheds: Des selected watersheds: Des

MoinesMoines

34

Nodaway Nodaway

38

Scenario MapsScenario Maps

40

Distributions of options Distributions of options (alleles) and practices(alleles) and practices

NodawayWatershed distribution of options

0

100

200

300

400

500

600

700

Sq

. km

Focus on N

Focus on P and N

NodawayWatershed distribution by practice

0

200

400

600

800

1000

1200

CRP CS CT N reduction No Till Terrace Contouring

Sq

. km Focus on N

Focus on P, achieve both N and P

Baseline

41

Conclusions and Conclusions and Recommendations Recommendations

Significant reductions in both phosphorus and nitrogen Significant reductions in both phosphorus and nitrogen loadings can be achieved in all of the watersheds in loadings can be achieved in all of the watersheds in the statethe state The costs are significantThe costs are significant But, much smaller than they would be if didn’t carefully select But, much smaller than they would be if didn’t carefully select

which practices go where (targeting)which practices go where (targeting)

Focus on N alone produces a markedly different Focus on N alone produces a markedly different watershed configuration than when the focus is both watershed configuration than when the focus is both on P and Non P and N

Practices which are efficient for phosphorus and Practices which are efficient for phosphorus and erosion control are, in general, not efficient in erosion control are, in general, not efficient in controlling nitrogencontrolling nitrogen If we wish to focus to both nutrients, combining traditional If we wish to focus to both nutrients, combining traditional

structural practice with measures directly targeting nitrogen structural practice with measures directly targeting nitrogen will be necessarywill be necessary

42

Caveats and Research Caveats and Research NeedsNeeds

Inclusion of other options will very likely alter resultsInclusion of other options will very likely alter results Results needed to be interpreted with cautionResults needed to be interpreted with caution

E.g., we do not recommend actual removal of conservation E.g., we do not recommend actual removal of conservation practices or abandonment of conservation tillagepractices or abandonment of conservation tillage

Lack of detailed spatial data only allows identification Lack of detailed spatial data only allows identification of desired conservation option mix at the subbasin of desired conservation option mix at the subbasin levellevel

Better hydrologic, water quality, land use, and farm-Better hydrologic, water quality, land use, and farm-level data would help to add realism to the analysislevel data would help to add realism to the analysis

Studying sensitivity of the results to changes in costs, Studying sensitivity of the results to changes in costs, efficiencies of conservation practices and weather efficiencies of conservation practices and weather conditions would be very helpful in providingconditions would be very helpful in providing

43

Continuing WorkContinuing Work Sergey Rabotyagov’s PhD thesis, Iowa Sergey Rabotyagov’s PhD thesis, Iowa

updatesupdates 2007 land and corn prices2007 land and corn prices Added grassed waterways as an optionAdded grassed waterways as an option Continued improvements to SWATContinued improvements to SWAT 30% N and P reductions ~ $300 million/yr cost30% N and P reductions ~ $300 million/yr cost

UMRB work (also Sergey)UMRB work (also Sergey) Smaller watershed work (field scale)Smaller watershed work (field scale)

Walnut Creek (CEAP project – USDA)Walnut Creek (CEAP project – USDA) Boone (USDA-CSREES)Boone (USDA-CSREES)

Application of GA for biofuels sustainabilityApplication of GA for biofuels sustainability