snow.c
| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | //----------------------------------------------------------------------------- | ||
| 2 | // snow.c | ||
| 3 | // | ||
| 4 | // Project: EPA SWMM5 | ||
| 5 | // Version: 5.2 | ||
| 6 | // Date: 11/01/21 (Build 5.2.0) | ||
| 7 | // Author: L. Rossman | ||
| 8 | // | ||
| 9 | // Models snow melt processes. | ||
| 10 | // | ||
| 11 | // Update History | ||
| 12 | // ============== | ||
| 13 | // Build 5.1.008: | ||
| 14 | // - Adjustment of snowmelt and subcatchment's net precipitation for area | ||
| 15 | // covered by snow was corrected. | ||
| 16 | // - Area covered by snow now included in calculation of rate that liquid | ||
| 17 | // water leaves a snowpack. | ||
| 18 | // Build 5.2.0: | ||
| 19 | // - Subcatchment snow pack area should not include LID area. | ||
| 20 | //----------------------------------------------------------------------------- | ||
| 21 | #define _CRT_SECURE_NO_DEPRECATE | ||
| 22 | |||
| 23 | #include <stdlib.h> | ||
| 24 | #include <string.h> | ||
| 25 | #include <math.h> | ||
| 26 | #include "headers.h" | ||
| 27 | |||
| 28 | //----------------------------------------------------------------------------- | ||
| 29 | // Constants | ||
| 30 | //----------------------------------------------------------------------------- | ||
| 31 | // These symbolize the keywords listed in SnowmeltWords in keywords.c | ||
| 32 | enum SnowKeywords {SNOW_PLOWABLE, SNOW_IMPERV, SNOW_PERV, SNOW_REMOVAL}; | ||
| 33 | |||
| 34 | //----------------------------------------------------------------------------- | ||
| 35 | // External functions (declared in funcs.h) | ||
| 36 | //----------------------------------------------------------------------------- | ||
| 37 | // snow_createSnowpack (called from subcatch_setParams) | ||
| 38 | // snow_initSnowpack (called from subcatch_initState) | ||
| 39 | // snow_initSnowmelt (called from createObjects in project.c) | ||
| 40 | // snow_validateSnowmelt(called from project_validate) | ||
| 41 | // snow_readMeltParams (called from parseLine in input.c) | ||
| 42 | // snow_setMeltCoeffs (called from setTemp in climate.c) | ||
| 43 | // snow_plowSnow (called from runoff_execute) | ||
| 44 | // snow_getSnowMelt (called from subcatch_getRunoff) | ||
| 45 | // snow_getSnowCover (called from massbal_open) | ||
| 46 | // snow_getState (called from saveRunoff in hotstart.c) | ||
| 47 | |||
| 48 | //----------------------------------------------------------------------------- | ||
| 49 | // Local functions | ||
| 50 | //----------------------------------------------------------------------------- | ||
| 51 | static void setMeltParams(int i, int k, double x[]); | ||
| 52 | static double getRainmelt(double rainfall); | ||
| 53 | static double getArealDepletion(TSnowpack* snowpack, int i, double snowfall, | ||
| 54 | double tStep); | ||
| 55 | static double getArealSnowCover(int i, double awesi); | ||
| 56 | static double meltSnowpack(TSnowpack* snowpack, int i, double rmelt, double asc, | ||
| 57 | double snowfall, double tStep); | ||
| 58 | static double reduceColdContent(TSnowpack* snowpack, int i, double smelt, | ||
| 59 | double ccFactor); | ||
| 60 | static double routeSnowmelt(TSnowpack* snowpack, int i, double smelt, double asc, | ||
| 61 | double rainfall, double tStep); | ||
| 62 | static void updateColdContent(TSnowpack* snowpack, int i, double asc, | ||
| 63 | double snowfall, double tStep); | ||
| 64 | |||
| 65 | |||
| 66 | //============================================================================= | ||
| 67 | |||
| 68 | 12 | int snow_readMeltParams(char* tok[], int ntoks) | |
| 69 | // | ||
| 70 | // Input: tok[] = array of string tokens | ||
| 71 | // ntoks = number of tokens | ||
| 72 | // Output: returns error code | ||
| 73 | // Purpose: reads snow melt parameters from a tokenized line of input data. | ||
| 74 | // | ||
| 75 | // Format of data are: | ||
| 76 | // Name SubArea Cmin Cmax Tbase FWF SD0 FW0 SNN0/SD100 | ||
| 77 | // Name REMOVAL SDplow Fout Fimperv Fperv Fimelt Fsubcatch (Subcatch) | ||
| 78 | // | ||
| 79 | { | ||
| 80 | int i, j, k, m, n; | ||
| 81 | double x[7]; | ||
| 82 |
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12 | if ( ntoks < 8 ) return error_setInpError(ERR_ITEMS, ""); |
| 83 | |||
| 84 | // --- save snow melt parameter set name if not already done so | ||
| 85 | 12 | j = project_findObject(SNOWMELT, tok[0]); | |
| 86 |
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12 | if ( j < 0 ) return error_setInpError(ERR_NAME, tok[0]); |
| 87 |
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12 | if ( Snowmelt[j].ID == NULL ) |
| 88 | 3 | Snowmelt[j].ID = project_findID(SNOWMELT, tok[0]); | |
| 89 | |||
| 90 | // --- identify data keyword | ||
| 91 | 12 | k = findmatch(tok[1], SnowmeltWords); | |
| 92 |
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12 | if ( k < 0 ) return error_setInpError(ERR_KEYWORD, tok[1]); |
| 93 | |||
| 94 | // --- number of parameters to read | ||
| 95 | 12 | n = 7; // 7 for subareas | |
| 96 |
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12 | if ( k == SNOW_REMOVAL ) n = 6; // 6 for Removal |
| 97 |
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12 | if ( ntoks < n + 2 ) return error_setInpError(ERR_ITEMS, ""); |
| 98 |
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96 | for (i=0; i<7; i++) x[i] = 0.0; |
| 99 | |||
| 100 | // --- parse each parameter | ||
| 101 |
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93 | for (i=0; i<n; i++) |
| 102 | { | ||
| 103 |
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81 | if ( ! getDouble(tok[i+2], &x[i]) ) |
| 104 | ✗ | return error_setInpError(ERR_NUMBER, tok[i+2]); | |
| 105 | } | ||
| 106 | |||
| 107 | // --- parse name of subcatch receiving snow plowed from current subcatch | ||
| 108 |
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12 | if ( k == SNOW_REMOVAL ) |
| 109 | { | ||
| 110 | 3 | x[6] = -1.0; | |
| 111 |
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3 | if ( ntoks >= 9 ) |
| 112 | { | ||
| 113 | ✗ | m = project_findObject(SUBCATCH, tok[8]); | |
| 114 | ✗ | if ( m < 0 ) return error_setInpError(ERR_NAME, tok[8]); | |
| 115 | ✗ | x[6] = m; | |
| 116 | } | ||
| 117 | } | ||
| 118 | |||
| 119 | // --- save snow melt parameters | ||
| 120 | 12 | setMeltParams(j, k, x); | |
| 121 | 12 | return 0; | |
| 122 | } | ||
| 123 | |||
| 124 | //============================================================================= | ||
| 125 | |||
| 126 | 3 | int snow_createSnowpack(int j, int k) | |
| 127 | // | ||
| 128 | // Input: j = subcatchment index | ||
| 129 | // k = snow melt parameter set index | ||
| 130 | // Output: returns TRUE if successful | ||
| 131 | // Purpose: creates a snowpack object for a subcacthment. | ||
| 132 | // | ||
| 133 | { | ||
| 134 | TSnowpack* snowpack; | ||
| 135 | 3 | snowpack = (TSnowpack *) malloc(sizeof(TSnowpack)); | |
| 136 |
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3 | if ( !snowpack ) return FALSE; |
| 137 | 3 | Subcatch[j].snowpack = snowpack; | |
| 138 | 3 | snowpack->snowmeltIndex = k; | |
| 139 | 3 | return TRUE; | |
| 140 | } | ||
| 141 | |||
| 142 | //============================================================================= | ||
| 143 | |||
| 144 | 3 | void snow_initSnowpack(int j) | |
| 145 | // | ||
| 146 | // Input: j = subcatchment index | ||
| 147 | // Output: none | ||
| 148 | // Purpose: initializes state of a subcatchment's snow pack. | ||
| 149 | // | ||
| 150 | { | ||
| 151 | int i; // snow sub-area index | ||
| 152 | int k; // snowmelt parameter set index | ||
| 153 | double f; // fraction of impervious area plowable | ||
| 154 | 3 | double snowDepth = 0.0; // snow depth on entire subcatchment (ft) | |
| 155 | TSnowpack* snowpack; // ptr. to snow pack object | ||
| 156 | |||
| 157 | // --- get ptr. to subcatchment's snow pack object | ||
| 158 | 3 | snowpack = Subcatch[j].snowpack; | |
| 159 |
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3 | if ( snowpack == NULL ) return; |
| 160 | |||
| 161 | // --- identify index of snow melt data set used by snow pack | ||
| 162 | 3 | k = Subcatch[j].snowpack->snowmeltIndex; | |
| 163 | |||
| 164 | // --- find fractional area of each snow surface | ||
| 165 | 3 | f = Snowmelt[k].snn; | |
| 166 | 3 | snowpack->fArea[SNOW_PLOWABLE] = f * Subcatch[j].fracImperv; | |
| 167 | 3 | snowpack->fArea[SNOW_IMPERV] = (1.0 - f) * Subcatch[j].fracImperv; | |
| 168 | 3 | snowpack->fArea[SNOW_PERV] = 1.0 - Subcatch[j].fracImperv; | |
| 169 | |||
| 170 | // --- initialize state of snow pack on each snow surface | ||
| 171 |
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12 | for (i=SNOW_PLOWABLE; i<=SNOW_PERV; i++) |
| 172 | { | ||
| 173 |
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9 | if ( snowpack->fArea[i] > 0.0 ) |
| 174 | { | ||
| 175 | 6 | snowpack->wsnow[i] = Snowmelt[k].wsnow[i]; | |
| 176 | 6 | snowpack->fw[i] = Snowmelt[k].fwnow[i]; | |
| 177 | } | ||
| 178 | else | ||
| 179 | { | ||
| 180 | 3 | snowpack->wsnow[i] = 0.0; | |
| 181 | 3 | snowpack->fw[i] = 0.0; | |
| 182 | } | ||
| 183 | 9 | snowpack->coldc[i] = 0.0; | |
| 184 | 9 | snowpack->ati[i] = Snowmelt[k].tbase[i]; | |
| 185 | 9 | snowpack->awe[i] = 1.0; | |
| 186 | 9 | snowDepth += snowpack->wsnow[i] * snowpack->fArea[i]; | |
| 187 | } | ||
| 188 | 3 | Subcatch[j].newSnowDepth = snowDepth; | |
| 189 | } | ||
| 190 | |||
| 191 | //============================================================================= | ||
| 192 | |||
| 193 | 3 | void snow_initSnowmelt(int j) | |
| 194 | // | ||
| 195 | // Input: j = snowmelt parameter set index | ||
| 196 | // Output: none | ||
| 197 | // Purpose: initializes values in a snow melt parameter set. | ||
| 198 | // | ||
| 199 | { | ||
| 200 | int i, k; | ||
| 201 |
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12 | for (i=0; i<3; i++) |
| 202 | { | ||
| 203 | 9 | Snowmelt[j].snn = 0.0; | |
| 204 | 9 | Snowmelt[j].si[i] = 0.0; | |
| 205 | 9 | Snowmelt[j].dhmin[i] = 0.0; | |
| 206 | 9 | Snowmelt[j].dhmax[i] = 0.0; | |
| 207 | 9 | Snowmelt[j].tbase[i] = 0.0; | |
| 208 | 9 | Snowmelt[j].fwfrac[i] = 0.0; | |
| 209 | 9 | Snowmelt[j].wsnow[i] = 0.0; | |
| 210 | 9 | Snowmelt[j].fwnow[i] = 0.0; | |
| 211 | 9 | Snowmelt[j].weplow = 1.0e6; | |
| 212 |
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54 | for (k=0; k<5; k++) Snowmelt[j].sfrac[k] = 0.0; |
| 213 | 9 | Snowmelt[j].toSubcatch = -1; | |
| 214 | } | ||
| 215 | 3 | } | |
| 216 | |||
| 217 | //============================================================================= | ||
| 218 | |||
| 219 | 3 | void snow_validateSnowmelt(int j) | |
| 220 | // | ||
| 221 | // Input: j = snowmelt parameter set index | ||
| 222 | // Output: none | ||
| 223 | // Purpose: checks for valid values in a snow melt parameter set. | ||
| 224 | // | ||
| 225 | { | ||
| 226 | int k; | ||
| 227 | 3 | char err = FALSE; | |
| 228 | 3 | double sum = 0.0; | |
| 229 | |||
| 230 |
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12 | for ( k = SNOW_PLOWABLE; k <= SNOW_PERV; k++ ) |
| 231 | { | ||
| 232 | // --- check melt coeffs. | ||
| 233 |
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9 | if ( Snowmelt[j].dhmin[k] > Snowmelt[j].dhmax[k] ) err = TRUE; |
| 234 | |||
| 235 | // --- check free water fraction | ||
| 236 |
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9 | if ( Snowmelt[j].fwfrac[k] < 0.0 || |
| 237 |
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9 | Snowmelt[j].fwfrac[k] > 1.0) err = TRUE; |
| 238 | } | ||
| 239 | |||
| 240 | // --- check fraction of imperv. area plowable | ||
| 241 |
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3 | if ( Snowmelt[j].snn < 0.0 || Snowmelt[j].snn > 1.0 ) err = TRUE; |
| 242 | |||
| 243 | // --- check that removal fractions sum <= 1.0 | ||
| 244 |
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18 | for ( k=0; k<5; k++ ) sum += Snowmelt[j].sfrac[k]; |
| 245 |
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3 | if ( sum > 1.01 ) err = TRUE; |
| 246 |
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3 | if ( err ) report_writeErrorMsg(ERR_SNOWPACK_PARAMS, Snowmelt[j].ID); |
| 247 | 3 | } | |
| 248 | |||
| 249 | //============================================================================= | ||
| 250 | |||
| 251 | ✗ | void snow_getState(int i, int j, double x[]) | |
| 252 | // | ||
| 253 | // Input: i = subcatchment index | ||
| 254 | // j = snow pack sub-area index | ||
| 255 | // Output: updates array of snow pack state variables x | ||
| 256 | // Purpose: retrieves the current state of a snow pack object. | ||
| 257 | // | ||
| 258 | { | ||
| 259 | ✗ | TSnowpack* snowpack = Subcatch[i].snowpack; | |
| 260 | ✗ | if ( snowpack == NULL ) return; | |
| 261 | ✗ | x[0] = snowpack->wsnow[j]; | |
| 262 | ✗ | x[1] = snowpack->fw[j]; | |
| 263 | ✗ | x[2] = snowpack->coldc[j]; | |
| 264 | ✗ | x[3] = snowpack->ati[j]; | |
| 265 | ✗ | x[4] = snowpack->awe[j]; | |
| 266 | } | ||
| 267 | |||
| 268 | //============================================================================= | ||
| 269 | |||
| 270 | ✗ | void snow_setState(int i, int j, double x[]) | |
| 271 | // | ||
| 272 | // Input: i = subcatchment index | ||
| 273 | // j = snow pack sub-area index | ||
| 274 | // x = array of snow pack state variables | ||
| 275 | // Output: none | ||
| 276 | // Purpose: sets the current state of a snow pack object. | ||
| 277 | // | ||
| 278 | { | ||
| 279 | ✗ | TSnowpack* snowpack = Subcatch[i].snowpack; | |
| 280 | ✗ | if ( snowpack == NULL ) return; | |
| 281 | ✗ | snowpack->wsnow[j] = x[0]; | |
| 282 | ✗ | snowpack->fw[j] = x[1]; | |
| 283 | ✗ | snowpack->coldc[j] = x[2]; | |
| 284 | ✗ | snowpack->ati[j] = x[3]; | |
| 285 | ✗ | snowpack->awe[j] = x[4]; | |
| 286 | } | ||
| 287 | |||
| 288 | //============================================================================= | ||
| 289 | |||
| 290 | 12 | void setMeltParams(int j, int k, double x[]) | |
| 291 | // | ||
| 292 | // Input: j = snowmelt parameter set index | ||
| 293 | // k = data category index | ||
| 294 | // x = array of snow parameter values | ||
| 295 | // Output: none | ||
| 296 | // Purpose: assigns values to parameters in a snow melt data set. | ||
| 297 | // | ||
| 298 | { | ||
| 299 | int i; | ||
| 300 | |||
| 301 | // --- snow pack melt parameters | ||
| 302 |
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12 | if ( k >= SNOW_PLOWABLE && k <= SNOW_PERV ) |
| 303 | { | ||
| 304 | // --- min/max melt coeffs. | ||
| 305 | 9 | Snowmelt[j].dhmin[k] = x[0] * UCF(TEMPERATURE) / UCF(RAINFALL); | |
| 306 | 9 | Snowmelt[j].dhmax[k] = x[1] * UCF(TEMPERATURE) / UCF(RAINFALL); | |
| 307 | |||
| 308 | // --- base melt temp (deg F) | ||
| 309 | 9 | Snowmelt[j].tbase[k] = x[2]; | |
| 310 |
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9 | if ( UnitSystem == SI ) |
| 311 | ✗ | Snowmelt[j].tbase[k] = (9./5.) * Snowmelt[j].tbase[k] + 32.0; | |
| 312 | |||
| 313 | // --- free water fractions | ||
| 314 | 9 | Snowmelt[j].fwfrac[k] = x[3]; | |
| 315 | |||
| 316 | // --- initial snow depth & free water depth | ||
| 317 | 9 | Snowmelt[j].wsnow[k] = x[4] / UCF(RAINDEPTH); | |
| 318 |
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9 | x[5] = MIN(x[5], (x[3]*x[4])); |
| 319 | 9 | Snowmelt[j].fwnow[k] = x[5] / UCF(RAINDEPTH); | |
| 320 | |||
| 321 | // --- fraction of impervious area that is plowable | ||
| 322 |
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9 | if ( k == SNOW_PLOWABLE ) Snowmelt[j].snn = x[6]; |
| 323 | |||
| 324 | // --- min. depth for 100% areal coverage on remaining | ||
| 325 | // impervious area or total pervious area | ||
| 326 | 6 | else Snowmelt[j].si[k] = x[6] / UCF(RAINDEPTH); | |
| 327 | } | ||
| 328 | |||
| 329 | // --- removal parameters | ||
| 330 |
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3 | else if ( k == SNOW_REMOVAL ) |
| 331 | { | ||
| 332 | 3 | Snowmelt[j].weplow = x[0] / UCF(RAINDEPTH); | |
| 333 |
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18 | for (i=0; i<=4; i++) Snowmelt[j].sfrac[i] = x[i+1]; |
| 334 |
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3 | if ( x[6] >= 0.0 ) Snowmelt[j].toSubcatch = (int)(x[6] + 0.01); |
| 335 | 3 | else Snowmelt[j].toSubcatch = -1; | |
| 336 | } | ||
| 337 | 12 | } | |
| 338 | |||
| 339 | //============================================================================= | ||
| 340 | |||
| 341 | 6 | void snow_setMeltCoeffs(int j, double s) | |
| 342 | // | ||
| 343 | // Input: j = snowmelt parameter set index | ||
| 344 | // s = snow season of year | ||
| 345 | // Output: none | ||
| 346 | // Purpose: sets values of snow melt coeffs. for particular time of year. | ||
| 347 | // | ||
| 348 | { | ||
| 349 | int k; // snow sub-area index | ||
| 350 | |||
| 351 |
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24 | for (k=SNOW_PLOWABLE; k<=SNOW_PERV; k++) |
| 352 | { | ||
| 353 | 18 | Snowmelt[j].dhm[k] = 0.5 * (Snowmelt[j].dhmax[k] * (1.0 + s) | |
| 354 | 18 | + Snowmelt[j].dhmin[k] * (1.0 - s)); | |
| 355 | } | ||
| 356 | 6 | } | |
| 357 | |||
| 358 | //============================================================================= | ||
| 359 | |||
| 360 | 3540 | void snow_plowSnow(int j, double tStep) | |
| 361 | // | ||
| 362 | // Input: j = subcatchment index | ||
| 363 | // tStep = time step (sec) | ||
| 364 | // Output: none | ||
| 365 | // Purpose: adds new snow to subcatchment and plows it between sub-areas. | ||
| 366 | // | ||
| 367 | { | ||
| 368 | int i; // snow sub-area index | ||
| 369 | int k; // snowmelt parameter set index | ||
| 370 | int m; // subcatchment index | ||
| 371 | double rainfall; // rainfall (not used) | ||
| 372 | double snowfall; // snowfall (ft/sec) | ||
| 373 | double exc; // excess snow depth (ft) | ||
| 374 | double f; // area ratio | ||
| 375 | double sfracTotal; // total fraction of snow moved | ||
| 376 | TSnowpack* snowpack; // ptr. to snow pack object | ||
| 377 | |||
| 378 | 3540 | snowpack = Subcatch[j].snowpack; | |
| 379 |
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3540 | if ( !snowpack ) return; |
| 380 | |||
| 381 | // --- see if there's any snowfall | ||
| 382 | 3540 | gage_getPrecip(Subcatch[j].gage, &rainfall, &snowfall); | |
| 383 | |||
| 384 | // --- add snowfall to snow pack | ||
| 385 |
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14160 | for (i=SNOW_PLOWABLE; i<=SNOW_PERV; i++) |
| 386 | { | ||
| 387 |
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10620 | if ( snowpack->fArea[i] > 0.0 ) |
| 388 | { | ||
| 389 | 7080 | snowpack->wsnow[i] += snowfall * tStep; | |
| 390 | 7080 | snowpack->imelt[i] = 0.0; | |
| 391 | } | ||
| 392 | } | ||
| 393 | |||
| 394 | // --- see if there is excess snow on plowable area to remove | ||
| 395 |
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3540 | if ( snowpack->fArea[SNOW_PLOWABLE] > 0.0 ) |
| 396 | { | ||
| 397 | ✗ | k = snowpack->snowmeltIndex; | |
| 398 | ✗ | if ( snowpack->wsnow[SNOW_PLOWABLE] >= Snowmelt[k].weplow ) | |
| 399 | { | ||
| 400 | // --- excess snow to be reomoved | ||
| 401 | ✗ | exc = snowpack->wsnow[SNOW_PLOWABLE]; | |
| 402 | |||
| 403 | // --- plow out of system | ||
| 404 | ✗ | f = snowpack->fArea[SNOW_PLOWABLE] * | |
| 405 | ✗ | (Subcatch[j].area - Subcatch[j].lidArea); | |
| 406 | ✗ | Snow.removed += Snowmelt[k].sfrac[0] * exc * f; | |
| 407 | ✗ | sfracTotal = Snowmelt[k].sfrac[0]; | |
| 408 | |||
| 409 | // --- plow onto non-plowable impervious area | ||
| 410 | ✗ | if ( snowpack->fArea[SNOW_IMPERV] > 0.0 ) | |
| 411 | { | ||
| 412 | ✗ | f = snowpack->fArea[SNOW_PLOWABLE] / | |
| 413 | ✗ | snowpack->fArea[SNOW_IMPERV]; | |
| 414 | ✗ | snowpack->wsnow[SNOW_IMPERV] += Snowmelt[k].sfrac[1] * exc * f; | |
| 415 | ✗ | sfracTotal += Snowmelt[k].sfrac[1]; | |
| 416 | } | ||
| 417 | |||
| 418 | // --- plow onto pervious area | ||
| 419 | ✗ | if ( snowpack->fArea[SNOW_PERV] > 0.0 ) | |
| 420 | { | ||
| 421 | ✗ | f = snowpack->fArea[SNOW_PLOWABLE] / | |
| 422 | ✗ | snowpack->fArea[SNOW_PERV]; | |
| 423 | ✗ | snowpack->wsnow[SNOW_PERV] += Snowmelt[k].sfrac[2] * exc * f; | |
| 424 | ✗ | sfracTotal += Snowmelt[k].sfrac[2]; | |
| 425 | } | ||
| 426 | |||
| 427 | // --- convert to immediate melt | ||
| 428 | ✗ | snowpack->imelt[SNOW_PLOWABLE] = Snowmelt[k].sfrac[3] * exc / tStep; | |
| 429 | ✗ | sfracTotal += Snowmelt[k].sfrac[3]; | |
| 430 | |||
| 431 | // --- send to another subcatchment | ||
| 432 | ✗ | if ( Snowmelt[k].sfrac[4] > 0.0 ) | |
| 433 | { | ||
| 434 | ✗ | m = Snowmelt[k].toSubcatch; | |
| 435 | ✗ | if ( Subcatch[m].snowpack ) | |
| 436 | { | ||
| 437 | ✗ | f = Subcatch[m].snowpack->fArea[SNOW_PERV]; | |
| 438 | } | ||
| 439 | ✗ | else f = 0.0; | |
| 440 | ✗ | if ( f > 0.0 ) | |
| 441 | { | ||
| 442 | ✗ | f = snowpack->fArea[SNOW_PLOWABLE] / f; | |
| 443 | ✗ | Subcatch[m].snowpack->wsnow[SNOW_PERV] += | |
| 444 | ✗ | Snowmelt[k].sfrac[4] * exc * f; | |
| 445 | ✗ | sfracTotal += Snowmelt[k].sfrac[4]; | |
| 446 | } | ||
| 447 | } | ||
| 448 | |||
| 449 | // --- reduce snow depth by amount plowed | ||
| 450 | ✗ | sfracTotal = MIN(sfracTotal, 1.0); | |
| 451 | ✗ | snowpack->wsnow[SNOW_PLOWABLE] = exc * (1.0 - sfracTotal); | |
| 452 | } | ||
| 453 | } | ||
| 454 | } | ||
| 455 | |||
| 456 | //============================================================================= | ||
| 457 | |||
| 458 | 3540 | double snow_getSnowMelt(int j, double rainfall, double snowfall, double tStep, | |
| 459 | double netPrecip[]) | ||
| 460 | // | ||
| 461 | // Input: j = subcatchment index | ||
| 462 | // rainfall = rainfall (ft/sec) | ||
| 463 | // snowfall = snowfall (ft/sec) | ||
| 464 | // tStep = time step (sec) | ||
| 465 | // Output: netPrecip = rainfall + snowmelt on each runoff sub-area (ft/sec), | ||
| 466 | // returns new snow depth over subcatchment | ||
| 467 | // Purpose: modifies rainfall input to subcatchment's sub-areas based on | ||
| 468 | // possible snow melt and updates snow depth over entire subcatchment. | ||
| 469 | // | ||
| 470 | { | ||
| 471 | int i; // snow sub-area index | ||
| 472 | double rmelt; // melt rate when rain falling (ft/sec) | ||
| 473 | double smelt; // snow melt from sub-area (ft/sec) | ||
| 474 | double asc; // frac. of sub-area snow covered | ||
| 475 | 3540 | double snowDepth = 0.0; // snow depth on entire subcatchment (ft) | |
| 476 | double impervPrecip; // net precip. on imperv. area (ft/sec) | ||
| 477 | TSnowpack* snowpack; // ptr. to snow pack object | ||
| 478 | |||
| 479 | // --- get ptr. to subcatchment's snowpack | ||
| 480 | 3540 | snowpack = Subcatch[j].snowpack; | |
| 481 | |||
| 482 | // --- compute snowmelt over entire subcatchment when rain falling | ||
| 483 | 3540 | rmelt = getRainmelt(rainfall); | |
| 484 | |||
| 485 | // --- compute snow melt from each type of subarea | ||
| 486 |
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14160 | for (i=SNOW_PLOWABLE; i<=SNOW_PERV; i++) |
| 487 | { | ||
| 488 | // --- completely melt pack if its depth is < 0.001 inch | ||
| 489 |
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10620 | if ( snowpack->wsnow[i] <= 0.001 / 12.0 ) |
| 490 | { | ||
| 491 | 6660 | asc = 0.0; | |
| 492 | 6660 | smelt = 0.0; | |
| 493 | 6660 | snowpack->imelt[i] += (snowpack->wsnow[i] + snowpack->fw[i]) | |
| 494 | 6660 | / tStep; | |
| 495 | 6660 | snowpack->wsnow[i] = 0.0; | |
| 496 | 6660 | snowpack->fw[i] = 0.0; | |
| 497 | 6660 | snowpack->coldc[i] = 0.0; | |
| 498 | } | ||
| 499 | |||
| 500 | // --- otherwise compute areal depletion, find snow melt | ||
| 501 | // and route it through pack | ||
| 502 | else | ||
| 503 | { | ||
| 504 | 3960 | asc = getArealDepletion(snowpack, i, snowfall, tStep); | |
| 505 | 3960 | smelt = meltSnowpack(snowpack, i, rmelt, asc, snowfall, tStep); | |
| 506 | 3960 | smelt = routeSnowmelt(snowpack, i, smelt, asc, rainfall, tStep); | |
| 507 | } | ||
| 508 | |||
| 509 | // --- find net precip. over entire subcatch area | ||
| 510 | 10620 | netPrecip[i] = smelt + snowpack->imelt[i] // snow pack melt | |
| 511 | 10620 | + rainfall*(1.0 - asc); // rainfall on non-snow area | |
| 512 | |||
| 513 | // --- add to total snow depth on subcatchment | ||
| 514 | 10620 | snowDepth += snowpack->wsnow[i] * snowpack->fArea[i]; | |
| 515 | } | ||
| 516 | |||
| 517 | // --- combine netPrecip on plowable & non-plowable imperv. areas | ||
| 518 |
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3540 | if ( Subcatch[j].fracImperv > 0.0 ) |
| 519 | { | ||
| 520 | 3540 | impervPrecip = | |
| 521 | 3540 | (netPrecip[SNOW_PLOWABLE] * snowpack->fArea[SNOW_PLOWABLE] + | |
| 522 | 3540 | netPrecip[SNOW_IMPERV] * snowpack->fArea[SNOW_IMPERV]) / | |
| 523 | 3540 | Subcatch[j].fracImperv; | |
| 524 | 3540 | netPrecip[IMPERV0] = impervPrecip; | |
| 525 | 3540 | netPrecip[IMPERV1] = impervPrecip; | |
| 526 | } | ||
| 527 | 3540 | return snowDepth; | |
| 528 | } | ||
| 529 | |||
| 530 | //============================================================================= | ||
| 531 | |||
| 532 | 192 | double snow_getSnowCover(int j) | |
| 533 | // | ||
| 534 | // Input: j = subcatchment index | ||
| 535 | // Output: returns volume of snow cover (ft3) | ||
| 536 | // Purpose: computes volume of snow on a subcatchment. | ||
| 537 | // | ||
| 538 | { | ||
| 539 | int i; | ||
| 540 | 192 | double snowCover = 0.0; // snow cover volume (ft3) | |
| 541 | TSnowpack* snowpack; // ptr. to snowpack object | ||
| 542 | |||
| 543 | 192 | snowpack = Subcatch[j].snowpack; | |
| 544 |
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192 | if ( !snowpack ) return 0.0; |
| 545 |
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24 | for (i=SNOW_PLOWABLE; i<=SNOW_PERV; i++) |
| 546 | { | ||
| 547 | 18 | snowCover += (snowpack->wsnow[i] + snowpack->fw[i]) * | |
| 548 | 18 | snowpack->fArea[i]; | |
| 549 | } | ||
| 550 | 6 | return snowCover * (Subcatch[j].area - Subcatch[j].lidArea); | |
| 551 | } | ||
| 552 | |||
| 553 | //============================================================================= | ||
| 554 | |||
| 555 | 3960 | double getArealDepletion(TSnowpack* snowpack, int i, double snowfall, double tStep) | |
| 556 | // | ||
| 557 | // Input: snowpack = ptr. to snow pack object | ||
| 558 | // i = snow sub-area index | ||
| 559 | // snowfall = snow fall rate (ft/sec) | ||
| 560 | // tStep = time step (sec) | ||
| 561 | // Output: returns fraction of sub-area with snow cover | ||
| 562 | // Purpose: depletes snow covered area as snow pack melts. | ||
| 563 | // | ||
| 564 | { | ||
| 565 | int k; // index of snow melt parameter set | ||
| 566 | double asc; // fraction of area with 100% cover | ||
| 567 | double si; // snow depth at 100% cover | ||
| 568 | double awesi; // depth relative to depth at 100% cover | ||
| 569 | double awe; | ||
| 570 | double sba; | ||
| 571 | double sbws; | ||
| 572 | |||
| 573 | // --- plowable sub-area not subject to areal depletion | ||
| 574 |
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3960 | if ( i == SNOW_PLOWABLE ) return 1.0; |
| 575 | 3960 | k = snowpack->snowmeltIndex; | |
| 576 | 3960 | si = Snowmelt[k].si[i]; | |
| 577 | |||
| 578 | // --- no depletion if depth zero or above SI | ||
| 579 |
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|
3960 | if ( si == 0.0 || snowpack->wsnow[i] >= si ) |
| 580 | { | ||
| 581 | 831 | snowpack->awe[i] = 1.0; | |
| 582 | 831 | return 1.0; | |
| 583 | } | ||
| 584 |
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|
3129 | if ( snowpack->wsnow[i] == 0.0 ) |
| 585 | { | ||
| 586 | ✗ | snowpack->awe[i] = 1.0; | |
| 587 | ✗ | return 0.0; | |
| 588 | } | ||
| 589 | |||
| 590 | // --- case of new snowfall | ||
| 591 |
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3129 | if ( snowfall > 0.0 ) |
| 592 | { | ||
| 593 | 769 | awe = (snowpack->wsnow[i] - snowfall*tStep) / si; | |
| 594 |
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|
769 | awe = MAX(awe, 0.0); |
| 595 | 769 | sba = getArealSnowCover(i, awe); | |
| 596 | 769 | sbws = awe + (0.75*snowfall*tStep) / si; | |
| 597 |
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769 | sbws = MIN(sbws, 1.0); |
| 598 | 769 | snowpack->awe[i] = awe; | |
| 599 | 769 | snowpack->sba[i] = sba; | |
| 600 | 769 | snowpack->sbws[i] = sbws; | |
| 601 | 769 | return 1.0; | |
| 602 | } | ||
| 603 | |||
| 604 | // --- case of no new snow | ||
| 605 | else | ||
| 606 | { | ||
| 607 | 2360 | awe = snowpack->awe[i]; | |
| 608 | 2360 | sba = snowpack->sba[i]; | |
| 609 | 2360 | sbws = snowpack->sbws[i]; | |
| 610 | 2360 | awesi = snowpack->wsnow[i] / si; | |
| 611 | |||
| 612 | // --- relative snow depth is below start of new snow ADC | ||
| 613 |
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|
2360 | if ( awesi < snowpack->awe[i] ) |
| 614 | { | ||
| 615 | 1916 | snowpack->awe[i] = 1.0; | |
| 616 | 1916 | asc = getArealSnowCover(i, awesi); | |
| 617 | } | ||
| 618 | |||
| 619 | // --- relative snow depth is above end of new snow ADC | ||
| 620 |
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|
444 | else if ( awesi >= snowpack->sbws[i] ) |
| 621 | { | ||
| 622 | 432 | asc = 1.0; | |
| 623 | } | ||
| 624 | |||
| 625 | // --- relative snow depth is on new snow ADC | ||
| 626 | else | ||
| 627 | { | ||
| 628 | 12 | asc = sba + (1.0 - sba) / (sbws - awe) * (awesi - awe); | |
| 629 | } | ||
| 630 | 2360 | return asc; | |
| 631 | } | ||
| 632 | } | ||
| 633 | |||
| 634 | //============================================================================= | ||
| 635 | |||
| 636 | 2685 | double getArealSnowCover(int i, double awesi) | |
| 637 | // | ||
| 638 | // Input: i = snow sub-area index | ||
| 639 | // awesi = snow depth relative to depth at 100% snow cover | ||
| 640 | // Output: returns fraction of sub-area with snow cover | ||
| 641 | // Purpose: finds x-value on areal depletion curve (ADC) for given y-value. | ||
| 642 | // | ||
| 643 | // Note: Areal depletion curves are associated with a project's Snow | ||
| 644 | // data structure. They plot relative snow depth (awesi) | ||
| 645 | // as a function of snow covererd area fraction (asc) in 10 equal | ||
| 646 | // awesi increments between 0 and 1.0. | ||
| 647 | // | ||
| 648 | { | ||
| 649 | int k; // type of ADC (impervious or pervious) | ||
| 650 | int m; // interval on ADC | ||
| 651 | double asc1, asc2; // asc values at ends of interval | ||
| 652 | |||
| 653 | // --- determine which ADC to use | ||
| 654 |
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|
2685 | if ( i == SNOW_IMPERV ) k = 0; |
| 655 |
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1343 | else if ( i == SNOW_PERV ) k = 1; |
| 656 | ✗ | else return 1.0; | |
| 657 | |||
| 658 | // --- locate interval on ADC that bounds awesi | ||
| 659 |
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2685 | if ( awesi <= 0.0 ) return 0.0; |
| 660 |
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2685 | if ( awesi >= 0.9999 ) return 1.0; |
| 661 | 2685 | m = (int)(awesi*10.0 + 0.00001); | |
| 662 | |||
| 663 | // --- get asc values for either end of interval | ||
| 664 | 2685 | asc1 = Snow.adc[k][m]; | |
| 665 |
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2685 | if ( m >= 9) asc2 = 1.0; |
| 666 | 2685 | else asc2 = Snow.adc[k][m+1]; | |
| 667 | |||
| 668 | // --- return with interpolated asc value | ||
| 669 | 2685 | return asc1 + (asc2 - asc1) / 0.1 * (awesi - 0.1*(float)m); | |
| 670 | } | ||
| 671 | |||
| 672 | //============================================================================= | ||
| 673 | |||
| 674 | 3960 | double meltSnowpack(TSnowpack* snowpack, int i, double rmelt, double asc, | |
| 675 | double snowfall, double tStep) | ||
| 676 | // | ||
| 677 | // Input: snowpack = ptr. to snow pack object | ||
| 678 | // i = snow sub-area index | ||
| 679 | // rmelt = melt rate if raining (ft/sec) | ||
| 680 | // asc = fraction of area covered with snow | ||
| 681 | // snowfall = rate of snow fall (ft/sec) | ||
| 682 | // tStep = time step (sec) | ||
| 683 | // Output: returns snow melt rate (ft/sec) | ||
| 684 | // Purpose: computes rate of snow melt from snow sub-area. | ||
| 685 | // | ||
| 686 | { | ||
| 687 | int k; // snowmelt parameter set index | ||
| 688 | double smelt; // melt rate over sub-area (ft/sec) | ||
| 689 | double ccFactor; // cold content conversion factor | ||
| 690 | |||
| 691 | // --- if raining then use result found from getRainMelt | ||
| 692 | 3960 | k = snowpack->snowmeltIndex; | |
| 693 |
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3960 | if ( rmelt > 0.0 ) smelt = rmelt; |
| 694 | |||
| 695 | // --- else if air temp. >= base melt temp. then use degree-day eqn. | ||
| 696 |
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|
2422 | else if ( Temp.ta >= Snowmelt[k].tbase[i] ) |
| 697 | { | ||
| 698 | 938 | smelt = Snowmelt[k].dhm[i] * (Temp.ta - Snowmelt[k].tbase[i]); | |
| 699 | } | ||
| 700 | |||
| 701 | // --- otherwise alter cold content and return 0 | ||
| 702 | else | ||
| 703 | { | ||
| 704 | 1484 | updateColdContent(snowpack, i, asc, snowfall, tStep); | |
| 705 | 1484 | return 0.0; | |
| 706 | } | ||
| 707 | |||
| 708 | // --- adjust snowmelt for area of snow cover | ||
| 709 | 2476 | smelt *= asc; | |
| 710 | |||
| 711 | // --- reduce cold content of melting pack | ||
| 712 | 2476 | ccFactor = tStep * Snow.rnm * asc; | |
| 713 | 2476 | smelt = reduceColdContent(snowpack, i, smelt, ccFactor); | |
| 714 | 2476 | snowpack->ati[i] = Snowmelt[k].tbase[i]; | |
| 715 | 2476 | return smelt; | |
| 716 | } | ||
| 717 | |||
| 718 | //============================================================================= | ||
| 719 | |||
| 720 | 3540 | double getRainmelt(double rainfall) | |
| 721 | // | ||
| 722 | // Input: rainfall = rainfall rate (ft/sec) | ||
| 723 | // Output: returns snow melt rate (ft/sec) | ||
| 724 | // Purpose: computes rate of snow melt when rainfall occurs. | ||
| 725 | // | ||
| 726 | { | ||
| 727 | double uadj; // adjusted wind speed | ||
| 728 | double t1, t2, t3; | ||
| 729 | double smelt; // snow melt in in/hr | ||
| 730 | |||
| 731 | 3540 | rainfall = rainfall * 43200.0; // convert rain to in/hr | |
| 732 |
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3540 | if ( rainfall > 0.02 ) |
| 733 | { | ||
| 734 | 1514 | uadj = 0.006 * Wind.ws; | |
| 735 | 1514 | t1 = Temp.ta - 32.0; | |
| 736 | 1514 | t2 = 7.5 * Temp.gamma * uadj; | |
| 737 | 1514 | t3 = 8.5 * uadj * (Temp.ea - 0.18); | |
| 738 | 1514 | smelt = t1 * (0.001167 + t2 + 0.007 * rainfall) + t3; | |
| 739 | 1514 | return smelt / 43200.0; | |
| 740 | } | ||
| 741 | 2026 | else return 0.0; | |
| 742 | } | ||
| 743 | |||
| 744 | //============================================================================= | ||
| 745 | |||
| 746 | 1484 | void updateColdContent(TSnowpack* snowpack, int i, double asc, double snowfall, | |
| 747 | double tStep) | ||
| 748 | // | ||
| 749 | // Input: snowpack = ptr. to snow pack object | ||
| 750 | // i = snow sub-area index | ||
| 751 | // asc = fraction of area snow covered | ||
| 752 | // snowfall = snow fall rate (ft/sec) | ||
| 753 | // tStep = time step (sec) | ||
| 754 | // Output: none | ||
| 755 | // Purpose: updates cold content of snow pack under non-melting conditions. | ||
| 756 | // | ||
| 757 | { | ||
| 758 | int k; // snowmelt parameter set index | ||
| 759 | double ati; // antecdent temperature index (deg F) | ||
| 760 | double cc; // snow pack cold content (ft) | ||
| 761 | double ccMax; // max. possible cold content (ft) | ||
| 762 | double tipm; // adjusted ATI weighting factor | ||
| 763 | |||
| 764 | // --- retrieve ATI & CC from snow pack object | ||
| 765 | 1484 | ati = snowpack->ati[i]; | |
| 766 | 1484 | cc = snowpack->coldc[i]; | |
| 767 | |||
| 768 | // --- if snowing, ATI = snow (air) temperature | ||
| 769 |
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1484 | if ( snowfall * 43200.0 > 0.02) ati = Temp.ta; |
| 770 | else | ||
| 771 | { | ||
| 772 | // convert ATI weighting factor from 6-hr to tStep time basis | ||
| 773 | 1264 | tipm = 1.0 - pow(1.0 - Snow.tipm, tStep / (6.0*3600.0)); | |
| 774 | |||
| 775 | // update ATI | ||
| 776 | 1264 | ati += tipm * (Temp.ta - ati); | |
| 777 | } | ||
| 778 | |||
| 779 | // --- ATI cannot exceed snow melt base temperature | ||
| 780 | 1484 | k = snowpack->snowmeltIndex; | |
| 781 |
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1484 | ati = MIN(ati, Snowmelt[k].tbase[i]); |
| 782 | |||
| 783 | // --- update cold content | ||
| 784 | 1484 | cc += Snow.rnm * Snowmelt[k].dhm[i] * (ati - Temp.ta) * tStep * asc; | |
| 785 |
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1484 | cc = MAX(cc, 0.0); |
| 786 | |||
| 787 | // --- maximum cold content based on assumed specific heat of snow | ||
| 788 | // of 0.007 in. water equiv. per deg. F | ||
| 789 | 1484 | ccMax = snowpack->wsnow[i] * 0.007 / 12.0 * (Snowmelt[k].tbase[i] - ati); | |
| 790 |
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1484 | cc = MIN(cc, ccMax); |
| 791 | |||
| 792 | // --- assign updated values to snowpack | ||
| 793 | 1484 | snowpack->coldc[i] = cc; | |
| 794 | 1484 | snowpack->ati[i] = ati; | |
| 795 | 1484 | } | |
| 796 | |||
| 797 | //============================================================================= | ||
| 798 | |||
| 799 | 2476 | double reduceColdContent(TSnowpack* snowpack, int i, double smelt, double ccFactor) | |
| 800 | // | ||
| 801 | // Input: snowpack = ptr. to snowpack object | ||
| 802 | // i = snow sub-area index | ||
| 803 | // smelt = potential melt rate (ft/sec) | ||
| 804 | // ccFactor = cold content conversion factor | ||
| 805 | // Output: returns snow melt rate (ft/sec) | ||
| 806 | // Purpose: reduces cold content of snow pack adjusting melt rate accordingly. | ||
| 807 | // | ||
| 808 | { | ||
| 809 | double cc; // cold content of snow pack (ft) | ||
| 810 | |||
| 811 | 2476 | cc = snowpack->coldc[i]; | |
| 812 |
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2476 | if ( smelt * ccFactor > cc ) |
| 813 | { | ||
| 814 | 2458 | smelt -= cc / ccFactor; | |
| 815 | 2458 | cc = 0.0; | |
| 816 | } | ||
| 817 | else | ||
| 818 | { | ||
| 819 | 18 | cc -= smelt * ccFactor; | |
| 820 | 18 | smelt = 0.0; | |
| 821 | } | ||
| 822 | 2476 | snowpack->coldc[i] = cc; | |
| 823 | 2476 | return smelt; | |
| 824 | } | ||
| 825 | |||
| 826 | //============================================================================= | ||
| 827 | |||
| 828 | 3960 | double routeSnowmelt(TSnowpack* snowpack, int i, double smelt, double asc, | |
| 829 | double rainfall, double tStep) | ||
| 830 | // | ||
| 831 | // Input: snowpack = ptr. to snowpack object | ||
| 832 | // i = snow sub-area index | ||
| 833 | // smelt = snow melt rate (ft/sec) | ||
| 834 | // asc = fraction of area snow covered | ||
| 835 | // rainfall = rainfall rate (ft/sec) | ||
| 836 | // tStep = time step (sec) | ||
| 837 | // Output: returns rate of liquid snow melt leaving a snow pack (ft/sec) | ||
| 838 | // Purpose: routes snow melt through free water holding capacity of snow pack. | ||
| 839 | // | ||
| 840 | { | ||
| 841 | int k; // snowmelt parameter set index | ||
| 842 | double vmelt; // snow melt volume (ft) | ||
| 843 | |||
| 844 | // --- get volume of snowmelt over time step | ||
| 845 | 3960 | k = snowpack->snowmeltIndex; | |
| 846 | 3960 | vmelt = smelt * tStep; | |
| 847 |
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3960 | vmelt = MIN(vmelt, snowpack->wsnow[i]); |
| 848 | |||
| 849 | // --- reduce snow depth by volume of snowmelt | ||
| 850 | 3960 | snowpack->wsnow[i] -= vmelt; | |
| 851 | |||
| 852 | // --- add snowmelt volume and any rainfall on snow | ||
| 853 | // covered area of sub-area to snow pack's free water content | ||
| 854 | 3960 | snowpack->fw[i] += vmelt + rainfall * tStep * asc; | |
| 855 | |||
| 856 | // --- excess free water becomes liquid melt that leaves the pack | ||
| 857 | 3960 | vmelt = snowpack->fw[i] - Snowmelt[k].fwfrac[i] * snowpack->wsnow[i]; | |
| 858 |
2/2✓ Branch 0 taken 2613 times.
✓ Branch 1 taken 1347 times.
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3960 | vmelt = MAX(vmelt, 0.0); |
| 859 | |||
| 860 | // --- reduce free water by liquid melt volume and return liquid melt rate | ||
| 861 | 3960 | snowpack->fw[i] -= vmelt; | |
| 862 | 3960 | return vmelt / tStep; | |
| 863 | } | ||
| 864 | |||
| 865 | //============================================================================= | ||
| 866 |