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

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Presentation on theme: "1 Recharge on Non-irrigated Lands ESHMC 8 January 2008 B. Contor."— Presentation transcript:

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

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

3 3

4 4

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

6 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 7 (stolen from DDW003)

8 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 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

10 10

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

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

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

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

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

17 17 Everything up to this slide has described the status quo.

18 18 Everything from this slide forward talks about possible modifications.

19 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 Difficult Moderate

20 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 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 22 Alternate Algorithms - Concerns USGS (Bauer & Vaccaro?) –Quantabytes of data –Bazillions of parameters –Long-term average recharge

23 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 24 Alternate Algorithms - Concerns Langbein –Tends to give much lower results than other methods –Total annual recharge

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

26 26

27 27 Backup Slides

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

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

30 30 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 Non-irrigated recharge GIS raster Grid cells Amount of recharge depth for each grid cell (stolen from May Training)

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