Recharge on Non-irrigated Lands

1. Recharge on Non-irrigated Lands ESHMC 8 January 2008 B. Contor

2. Outline • Review of current calculations • Recharge tool review • PEST possibilities • Possible alternate methods

5. Current Calculation • Recharge = non-linear function of precipitation Transition precip = ( 1/NK)(1/(N-1)) If precip <= trans. precip. then Rechg = K * PrecipN else Rech = recharge at trans precip + (precip - trans precip) • 3 sets of parameters, • Lava rock • Thin soil • Thick soil

6. Current Calculation • Accounts for processes of lower winter ET and snowmelt accumulation by calculating all winter recharge in Feb. • This will require some adjustment for monthly stress periods • I think the adjustments are doable

7. (stolen from DDW003)

8. Current Calculation • Soil type 4 represents withdrawals for wetlands, cities & dryfarms • NIR rasters are calculated off-line, prior to running recharge tools. • NIR rasters are inputs to GIS recharge tool

9. User hands GIS tool five things: • Raster of non-irr recharge for each stress period • Map of irrigated lands • Map of model cells • soil-group map • starting multipliers for soil groups

11. GIS tool hands FORTRAN tool five things • total area in each cell • irrigated area in each cell • depth of NIR in each cell, for each stress period • predominant soil type in each cell • multipliers

12. .sol file Source of data 1 - new data 0 - no data -1 - use previous data Values 1-4 - soil type -9999 - no value Soils (stolen from May Training)

13. Non-irrigated recharge depth (ft) for each grid cell Source of data 1 - new data 0 - no data -1 - use previous data A -9999 value means a raster value was not available for the cell .nir file Recharge on non-irrigated lands (stolen from May Training)

14. MultipliersPest can be set up to touch these (though we didn't do this last time) 1 multiplier for each of 4 soil groups

15. FORTRAN tool calculates non-irrigated area in each cell: • For each stress period, FORTRAN tool calculates recharge on non-irrigated lands: non-irr. area = (total area) – (irrigated area) recharge = (non-irr. area) x (depth) x (multiplier)

16. PEST Possibilities • Use 4 existing multipliers to adjust NIR differently for each spatial dist. of cover type

17. Everything up to this slidehas described the status quo.

18. Everything from this slideforward talks aboutpossible modifications.

19. PEST Possibilities • Allow additional multipliers (chop cover types into regions) • Write little PEST-touchable utility to do the calculations & generate the *.nir input for FORTRAN tool • Modify FORTRAN tool to do the NIR calculations internally, with PEST-touchable hooks Easy Moderate Difficult

20. Changing NIR Algorithm • If we keep status-quo Recharge Tool processing, we can change offline calc. of NIR at will • If we have FORTRAN calculate NIR, we will be committed to a single calculation algorithm

21. Alternate Algorithms • USGS (Bauer & Vaccaro?) • physically-based calculation using soils, precip, runoff equations, ET... • SVRP (Bartolino) • daily soil water balance using ET and precip (Rick Allen has already done some of this for ESPA?) • Langbein • empirical relationship from nationwide data • Other?

22. Alternate Algorithms - Concerns • USGS (Bauer & Vaccaro?) • Quantabytes of data • Bazillions of parameters • Long-term average recharge

23. Alternate Algorithms - Concerns • SVRP (Bartolino) • Needs to be adjusted for snow accumulation and melting • Needs adjustment for topographic concentration of runoff • Sparse weather-station data for calculations

24. Alternate Algorithms - Concerns • Langbein • Tends to give much lower results than other methods • Total annual recharge

25. Alternate Algorithms - Concerns • Other? • We have to find or invent the method • We have to agree on it

27. Backup Slides

28. Current Calculation • Recharge = non-linear function of precipitation (stolen from DDW-003)

29. The NIR groups are based on 7 non-irrigated land-cover types

30. Non-irrigated recharge GIS raster Amount of recharge depth for each grid cell Grid cells Recharge on Non-irrigated Lands Relationship • Average non-irrigated recharge for each model cell • Non-irrigated recharge is calculated for every cell but will • only be used on non-irrigated lands • Grid cells where a raster value is not present are represented • as -9999 (stolen from May Training)