PRECIPITATION-RUNOFF MODELING SYSTEM (PRMS) STORM-MODE COMPONENTS

BASIC HYDROLOGIC MODEL Q = P - ET  S Runoff Precip Met Vars Ground Water Soil Moisture Reservoirs Basin Chars Snow & Ice Water use Soil Moisture Components

PRMS

HYDROLOGIC RESPONSE UNITS (HRUs)

HRUs as FLOW PLANES & CHANNELS (Storm Mode)

SOIL MOISTURE ACCRETION - DAILY MODE - STORM MODE infil(hru) = net_precip(hru) - sroff(hru) Point Infil (fr) fr = dI/dt = ksat * [1. + (ps /  fr)] Areal Infil (fin) qrp = (.5 * net_precip 2 / fr ) net_precip < fr qrp = net_precip - (.5 * fr) Otherwise fin = net_precip - qrp

INFILTRATION SOIL PROFILE wpsatfc moisture content depth true relations profile t 0 + Profile t 0

Darcy’s Law Applied to Profile depth h x p Total head = h + x + p di/dt = K [(h + x + p) / x] i I = x (m t -m 0 ) h<<p mtmt m0m0 di/dt = K (1. + [p (m t - m 0 ) / i][Green & Ampt]

INFILTRATION - STORM MODE Point Infil (FR) FR = dI/dt = ksat * [1. + (ps / I)]

Computation of PS

AREAL INFILTRATION (FIN) RE = (.5 * PTN 2 / FR ) PTN < FR RE = PTN - (.5 * FR) Otherwise FIN = PTN - RE

SURFACE RUNOFF h infil q net precip tt xx qq hh = re+ x

Finite Difference Scheme Nodes with known values time t distance x t0t0 t1t1 t2t2 xx Solution node

Overland Flow q d = q c + re  x - (  x/  t) ( h c -h a ) h d = ( q d /  ) 1/m  = m (  t /  x ) (q b / h b ) For  >= 1

Overland Flow h d = h b + re  x - (  t/  x) ( q a -q b ) q d =  h d m  = m (  t /  x ) (q b / h b ) For  < 1

CHANNEL FLOW  tt QQ xx += q

Finite Difference Scheme Nodes with known values t x t0t0 t1t1 t2t2 xx Solution node

Available Channel Types Rectangular Triangular Input width Input width from left and right bank to center line at one foot depth

RADAR DATA NEXRAD vs S-POL, Buffalo Creek, CO

Buffalo Creek Watershed, CO

PRMS

ANIMAS RIVER, CO SURFACE GW SUBSURFACE PREDICTED MEASURED

PRMS

SUBSURFACE FLOW = IN - (ssrcoef_lin * S) (ssrcoef_sq * S 2 ) dS dt IN Subsurface Reservoir Equation solved at dt time step using analytical solution

PRMS

GROUND-WATER FLOW gwres_flow= gwflow_coeff * gwres_stor soil_to_gw + ssr_to_gw Ground-water Reservoir Equation solved at 15 minute dt and pro rated to shorter dt as needed

SEDIMENT - OVERLAND FLOW tt xx  cq)  ch) = er + ef + h infil q net precip x Sediment conc (c)

Interrill Detachment & Transport - er er = kr * net_precip(hru) 2 * e - (hc * hbar 2 )

Rill Detachment & Transport - ef ef = kf * ( tc - tr) tc = transport capacity tr = current transport rate tc = mm * hbar en

SEDIMENT - CHANNEL FLOW  cA tt  cQ xx += sed_lat sed_lat cQ c

Reservoir Routing Linear Routing res_out = sfres_coef * sfres_stor Modified Puls Routing 2 * sto 2 + O 2 = (I 2 - I 1 ) + 2 * sto 1 tt tt - O 1