Originally drawn by the Department of Lands and Survey N.Z. and published by the N.Z. Met Service.

Actual evaporation is an estimated average annual value for 1960-2006. The values are calculated using AE = PE .* ( 1 + P/PE - (1+ (P/PE)^w)^(1./w) )whereAE = average annual actual evaporationPE = average annual potential evaporation (item 2 above)P = average annual precipitation (item 1 above)W = 4.35 (empirical constant value)

Originally drawn by the Department of Lands and Survey N.Z. and published by the N.Z. Met Service.

Field- Descriptionfor REC variablesNZReach-Unique national identifier. This is the data field that is used to join to other REC1 datasets where "NZREACH" is the unique identifier.Order-Stream orderField descriptionsfor HUC1. Runoff is represented by threefields"Localrunoff_mm_yr""Runoff_mm_yr""Flow_L_s"Localrunoff_mm_yr is the predicted mean annual runoff in mm/year from the local land area that drains to an REC reachRunoff_mm_yr is the predicted mean annual runoff in mm/year from the entire upstream catchment that drains to an REC reachFlow_L_s is the predicted mean flow in L/s from the entire upstream catchment that drains to an REC reachThese data are those published in Woods, R. A., J. Hendrikx, R. D. Henderson and A. B. Tait (2006). “Mean Flow Hydrology of New Zealand Rivers.” Journal of Hydrology (NZ) 45(2): 95-110.The research was funded through a FRST-funded project "Land Use Intensification: Sustainable Management of Water Quantity and Quality (C01X0304)"2. The fourflood statistics are calculated for every reach in the River Environment Classification network. These flood statistics were obtained for each REC reach by finding the centroid of the catchment that drains to every reach, and then looking up the mapped McKerchar and Pearson value at the centroid. For catchments draining the Southern Alps to the southeast from the Waimakariri to Fiordland, an upstream searching algorithm (which finds the reach with catchment rain close to the catchment average, and uses that location to obtain a value of the parameter) was used to mimic as far as practical McKerchar and Pearson's description at p17.The four flood statistics are:q_a_0_8_reach (mean annual flood divided by area to the power of 0.8 - has units of m3/s / (sqkm)^0.8 )q100_reach (ratio of 100-year flood to mean annual flood - dimensionless)Qbar_reach_cumecs (in units of m3/s)Q100_reach_cumecs (in units of m3/s)McKerchar, A. I. and C. P. Pearson (1989). Flood Frequency in New Zealand. Hydrology Centre Publication No. 20, DSIR Division of Water Sciences, Christchurch, N.Z. p87. Pearson, C. P. and A. I. McKerchar (1989). “Flood Estimation - A Revised Procedure.” Transactions of the Institution of Professional Engineers New Zealand 16(2/CE): 59-65. 3.The fields in this directory are the result of development of a low flow model for New Zealand.Thefourfields in the file are named"Areaa", "Qla_nmps","Qla_lps""RivName"Areaa is the accumulated catchment area draining to the reach.Qla_nmps is the predicted 7-day mean annual specific low flow from the catchment area draining to the reach, expressed as nm/s, or l/s/km^2.Qla_lps is the predicted 7-day mean annual low flow from the catchment area draining to the reach, expressed as L/s.RivName is the name of the waterway, (not all waterways are named).The fields describing NZmonthlyflowratios are the result of joining the island ratios as described below, to the REC by CSoF classes, for each island. It contains the following fields:Jan, Feb,Mar, Apr, May, Jun, Jul, Aug,Sep, Oct, Nov, DecThe values Jan, Feb etc are the ratios of monthly flow to mean flow.If you know that the long term mean flow of a Cool Dry Lowland river in the North Island is 20 m3/s, then this data predicts that the long-term mean flow in January is 20*0.16=3.2 m3/sField description for BookerBooker2014 contains three columns. These are predictions from the random forest method as described in Booker and Woods (2014), with mean daily flow data collated March 2013. MeanFlowCumecs = mean flow (m3s-1)MALFCumecs = 7-day mean annual low flow (m3s-1)MeanAnnualFloodCumecs = Mean Annual flood as calculated from mean daily flows (not instantaneous flows) (m3s-1)Booker, D.J.; Woods, R.A. 2014: Comparing and combining physically-based and empirically-based approaches for estimating the hydrology of ungauged catchments. Journal of Hydrology DOI: 10.1016/j.jhydrol.2013.11.007.

Field Description: NZReach Unique national identifierReachID Unique regional identifierTnode To node – used for network direction Fnode From node – used for network directionLength Length of river section (m)Climate Climate level classCSoF Source-of-Flow level classCSoFG Geology level classCSoFGL Land-Cover level classCSoFGLNP Network-Position level classCSoFGLNPVL Valley-Landform level classSrc_of_flw Source-of-Flow factor category Geology Geology factor category Landcover Land-Cover factor category Net_posn Network-Position factor categoryVly_Lfrm Valley-Landform factor categoryOrder Stream order The Field "NZREACH" is the unique field used for joining to all other REC1 data that is available, but not included in the variables above.