Analytical Model Of Rainfall Interception Research Articles

Fitting the revised Gash analytical model of rainfall interception to Mongolian Scots pines in Mu Us Sandy Land, China

A rainfall interception experiment was completed for Pinus sylvestris var. mongolica plots with stand densities ranging from 925 to 2700 plants ha−1 in Mu Us Sandy Land, China from June to September 2013. The revised Gash analytical model was then applied to the canopy interception of the Mongolian Scots pine plantations. During the experimental process, the incident rainfall (P), throughfall (Tf), and stemflow events (Sf) were collected and measured, and meteorological data were simultaneously obtained on site. The Penman-Monteith equation and Gash regression method were used to estimate the evaporation rate (E) from the saturated canopy. The classical revised Gash calculation procedure and Leyton-constraint method were applied to obtain the canopy storage capacity (S). Parameters such as E, S, stemflow partitioning coefficient (pt), and trunk storage capacity (St) were scaled to the canopy cover fraction per unit area: Ec, Sc, ptc, and Stc in the revised Gash analytical model, which was also used in the simulation of the rainall interception (Tf, Sf, and I). The proportions of the measured Tf, Sf, and I accounted for 62.82%, 1.13%, and 36.05% of P, respectively. The ratios of Ec to rainfall intensity (R), Sc, ptc, and Stc were 0.0260 (0.0458), 1.210 mm (2.006 mm), 0.0630, and 0.0486 mm, respectively, during the experimental period. The analytical model with Ec and Sc equal to 0.182 (Penman-Monteith equation) and 1.210 mm (classical revised Gash calculation procedure) accurately simulated the canopy interception of the Mongolian Scots pine plantations, and the canopy interception variation in the analytical model was sensitive to P, Sc, Stc, c, Ec, and R, but was relatively insensitive to ptc.

The modelling of rainfall interception in growing and dormant seasons for a pine plantation and a black locust plantation in semi-arid Northwest China

Interception loss can remove a significant portion of rainwater from forested ecosystems. Therefore, the quantification and modelling of interception loss are of significant importance if human and ecosystem water demands are to be balanced under a future changing climate. This is particularly true for semi-arid/arid regions, where afforestation has become an important ecological restoration measure to tackle desertification, poverty and climate change. However, quantification and modelling of interception loss of plantations in these regions have rarely been reported. In the present study, rainfall interception loss was quantified and modelled over a one-year period (January-December 2016) for a deciduous broad-leafed R. pseudoacacia plantation and an evergreen needle-leaf P. tabuliformis plantation (common afforestation tree species) situated in the semi-arid Loess Plateau of China. The stand age, density, canopy cover and leaf area index of R. pseudoacacia during the study period were 15 years, 2000 tree ha−1, 0.48 and 1.41 m2 m−2, respectively. The corresponding values for Pinus tabuliformis were 17 years, 1200 tree ha−1, 0.62 and 2.53 m2 m−2. The measured throughfall, stemflow and derived estimates of interception loss for R. pseudoacacia were 81.1%, 1.3% and 17.6%, respectively. The corresponding values for P. tabuliformis were 75.4%, 0.7% and 23.9%. Given that the weather conditions experienced by the two forest stands were similar, the observed higher interception loss for P. tabuliformis can be explained by the higher canopy storage capacity and wet canopy evaporation rate of this species. The revised Gash analytical model of rainfall interception was well calibrated and validated against field measurements and was able to simulate the cumulative interception loss at two forest stands accurately, and it also effectively captured the seasonal variation (leafed growing and leafless dormant seasons), provided that the optimized wet-canopy evaporation rates were used. The revised model was highly sensitive to the canopy storage capacity and changes in the ratio of mean wet canopy evaporation to mean rainfall intensity and less sensitive to canopy cover, but it was found to be fairly insensitive to the trunk storage capacity.

Rainfall interception by natural and planted forests in the Middle Mountains of Central Nepal

► Rainfall interception loss was measured and modelled for natural and planted forest. ► The difference in rainfall interception loss between the two forests was examined. ► The model simulates interception loss well under monsoonal montane conditions. ► The difference in interception loss is due to differences in LAI and tree density. ► The high annual interception loss from planted forest could affect dry season flows. Measurements of gross rainfall, throughfall and stemflow were made during the 2011 rainy season in an evergreen natural forest and in a planted pine forest located in complex topography in the Middle Mountains of Central Nepal. For the period of observation (20 June–9 September, 2011), measured throughfall, stemflow and derived interception loss in the natural forest were 76.2%, 1.4% and 22.4% of incident rainfall, respectively. Corresponding values for the pine plantation were 83.0%, 0.5% and 16.5%. The revised version of Gash’s analytical model of rainfall interception was calibrated and validated for the two stands, representing a first for montane sub-tropical monsoonal conditions. The results of the modelling corresponded well with observed values, provided an optimised value was used for the average wet-canopy evaporation rate. The model was subsequently used to calculate annual interception losses from the two forests. Modelled estimates of annual interception loss for the planted and natural forest were 291 mm and 319 mm and represented 19.4% and 22.6% of incident rainfall, respectively. The high interception loss from the planted forest is considered a contributory factor towards the observed decline in dry season streamflow following the reforestation of degraded hillsides in the Middle Mountains of Nepal.

Modelling rainfall interception loss in forest restoration trials in Panama

AbstractA modified Liu analytical model of rainfall interception (Ic) by tree canopies was evaluated using rainfall, throughfall and stemflow data collected from forest restoration trials in the Republic of Panama. The model uses an introduced approach to estimating the water storage capacities of tree boles, which has a more realistic physical basis than earlier iterations of the Liu model. Study species (Acacia mangium, Gliricidia sepium, Guazuma ulmifolia, Ochroma pyramidale, and Pachira quinata) were selected on the basis of differing leaf size and crown characteristics. Significant interspecific differences in both observed and simulated cumulative interception loss were found, with A. mangium intercepting more rainfall than other species. Errors between calculated and modelled cumulative Ic ranged from + 6·3% to + 30·5%, with modelled Ic always being the larger term. During‐event evaporation rates from the study trees were positively related to tree height, crown area, and basal diameter. Crown area and the storage capacity of tree boles were negatively correlated. The results of a sensitivity analysis suggested that the modified model was most sensitive to variations in during‐event evaporation rate. The implications of the model's sensitivity to during‐event evaporation and the importance of this mechanism of interception loss are discussed, while suggestions are provided that may lead to further improvements to the analytical model. Copyright © 2010 John Wiley & Sons, Ltd.

Fraction of incident rainfall within the canopy of a pure stand of Pinus armandii with revised Gash model in the Liupan Mountains of China

Summary The throughfall, stemflow and interception during the growing season (June–September) of 2005 were observed in a pure stand of natural Pinus armandii forest in the Liupan Mountains of northwestern China. The results indicate that of the 544.0 mm of cumulative gross rainfall generated by 15 sampled events, throughfall, stemflow and canopy interception were 462.2 mm (84.96%), 4.8 mm (0.88%), and 77.0 mm (14.15%), respectively. The revised Gash analytical model of rainfall interception was employed and the simulated interception values were close to the observed with an underestimation of 5.87%. Moreover, 39.48% and 55.24% of interception were evaporated from canopy in the stages of “during storms” and “after storms”, respectively. The revised Gash analytical model is highly sensitive to changes regarding canopy storage capacity (S), cover (c) and the climate parameters of rainfall intensity R and evaporation E ¯ .

Measuring and modelling the rainfall interception loss by hedgerows in southern England

Gross rainfall ( P G), net rainfall and stemflow were measured for nearly 3 years in two hedgerows in southern England. The width of the zone where net rainfall was affected by the hedgerows was equivalent to about two hedgerow heights. Rainfall interception was calculated as the difference between the volume of water, from gross rainfall, that would have reached the ground of the sampling area (which also included areas outside the canopy) without the presence of a hedgerow and the actual amount of net rainfall plus stemflow. Averaged over both hedgerows the interception loss during the period of full leaf cover was 57% of P G if related to the ground area covered by the hedgerow canopies or 24% of P G if related to the total ground area affected by the presence of the hedgerows. For the leafless period, the respective values were 49 and 19%. Stemflow constituted a small part in the water balance of the hedgerows and equalled 0.2% of P G in the summer and 0.5% of P G in the winter. Interception storage capacity, if related to projected canopy area, was 2.6 mm during the growing season and 1.2 mm in the leafless hedgerows. During many small rainstorms, which were often associated with high windspeeds, the hedgerows intercepted more rainwater than the amount that would have fallen on the ground covered by them without their presence. This caused the coefficient of free throughfall, when calculated per unit projected canopy area, to be negative. The original Gash [Gash, J.H.C., 1979. An analytical model of rainfall interception by forests. Quart. J. R. Meteorol. Soc. 105, 43–55] analytical model of rainfall interception was parameterised for the hedgerows and tested using data that had not been included in the parameterisation process. The Gash model predicted the interception loss of hedgerows from daily rainfall data with reasonable accuracy.

The importance of canopy structure in controlling the interception loss of rainfall: Examples from a young and an old-growth Douglas-fir forest

The canopy water storage capacity ( S), direct throughfall fraction ( p), the ratio of evaporation to rainfall intensity ( E ¯ / R ¯ ) and interception loss ( I n), of a Douglas-fir forest are influenced by short (seasonal) and long-term (decades to centuries) changes in the forest canopy. Gross precipitation (P G) and net precipitation (P n) were measured in a young (25-year-old) Douglas-fir forest and the results compared with measurements previously made in a nearby old-growth (>450-year-old) Douglas-fir forest [Link, T.E., Unsworth, M.H., Marks, D., 2004. The dynamics of rainfall interception by a seasonal temperate rainforest. Agric. Forest Meteorol. 124, 171–191.]. Canopy rainfall variables were estimated using a regression-based method that estimates S, p and E ¯ / R ¯ for individual storms using the relationship between P G and P n. The individual storm estimates of S, p and E ¯ / R ¯ for the young forest were applied to a rainfall interception model (Gash model [Gash, J.H.C., 1979. An analytical model of rainfall interception by forest. Q. J. R. Meteorol. Soc. 105, 43–55.]) to determine the effect of seasonal changes in canopy hydrologic variables have on estimates of I n (young forest only). The Gash model was previously applied to the old-growth forest [Link, T.E., Unsworth, M.H., Marks, D., 2004. The dynamics of rainfall interception by a seasonal temperate rainforest. Agric. Forest Meteorol. 124, 171–191.]. The young forest had significantly different S (1.40 mm ± 0.27) and p (0.12 ± 0.07) relative to the old-growth forest ( S = 3.32 ± 0.35; p = 0.42 ± 0.07). Seasonal variation in canopy structure, such as deciduous leaf senescence and coniferous needle drop, were correlated with decreases in S. The differences in S and p between the two forests resulted in an I n that was only slightly larger in the old-growth forest because the E ¯ / R ¯ for the two forests were similar (young = 0.18 ± 0.06; old-growth = 0.17 ± 0.08). E ¯ / R ¯ in the young and old-growth forests may have been similar because developmental changes associated with old-growth forest may alter the external resistance ( r a) and the effective area for evaporation. The Gash model successfully predicted I n for the young forest on a seasonal basis (3.29% error), but experienced larger errors (range = −91 to 36% error) for individual storms. The seasonal error and the error for individual storms improved when seasonal variations in canopy characteristics were incorporated in the model (seasonal error = 2.37%; individual storm error range = −12.0 to 21.7%). Therefore, short-term (seasonal) changes in phenology and long-term (decades to centuries) horizontal and vertical development of the forest canopy influence S, p, I n and E ¯ / R ¯ of Douglas-fir forests.

The importance of epiphytes to total rainfall interception by a tropical montane rain forest in Costa Rica

The abundant epiphyte vegetation of upper montane tropical rain forests, which in terms of biomass is mainly composed of non-vascular plants (mosses, liverworts and lichens), can be expected to influence the magnitude of canopy water fluxes such as rainfall interception. The objects of this study were to: (i) estimate stand canopy water storage characteristics, (ii) determine rainfall interception by the canopy as a whole, and (iii) adapt an analytical model of rainfall interception, to enable the quantification of the contribution by non-vascular epiphytes to total interception. The studied old-growth forest in the Cordillera de Talamanca, Costa Rica, was 35 m tall, dominated by oaks, and little affected by fog. The estimated leaf area index of the trees was 7.7 m 2 m −2, which combined with results from a leaf wetting experiment gave a tree leaf water storage capacity of 1.08 mm at the stand level. The biomass of non-vascular epiphytes amounted to 1.9 t ha −1 dry weight. Monthly moss water contents measured in situ ranged between 24 and 406% of moss dry weight, corresponding to a maximum moss water storage of 0.81 mm at stand level. Seasonal variation in moss water contents was reproduced satisfactorily by a running water balance model. A modified analytical interception model, which incorporated the moss water balance model, was applied. Weekly sums of observed throughfall, stemflow and interception measurements were available for comparison and amounted to 70, 2 and 28% of the associated 2150 mm of rain. The model predicted the observed values quite well and suggested that mosses contributed about 6% to the modelled interception total. Hence, the hydrological importance of epiphytes in the studied forest was rather limited despite their considerable maximum water storage capacity. This is thought to reflect the fact that under the prevailing rainfall conditions only a fraction of the potential storage is actually available.

Rainfall interception by a Pinus sylvestris forest patch overgrown in a Mediterranean mountainous abandoned area II. Assessment of the applicability of Gash's analytical model

A set of 147 rainstorms each exceeding 1 mm bulk rainfall was used to validate the Gash analytical model of rainfall interception in a Pinus sylvestris forest patch overgrown in an abandoned Mediterranean mountain area. The results seems to indicate that the Gash analytical model is sufficiently robust to be applicable in Mediterranean mountain conditions for obtaining long-term total interception losses, and that prediction errors are in the same range as those obtained in earlier validations of the model. In contrast, there is a marked difference between observed and predicted values comparing individual events.

Estimating sparse forest rainfall interception with an analytical model

Gash's analytical model of rainfall interception is reformulated, with improved boundary conditions, to give a better description of the evaporation from sparse forest. The model is tested against data from Les Landes Forest collected during HAPEX-MOBILHY. The new formulation requires an estimate of the evaporation per unit area of canopy, rather than per unit ground area. When the evaporation per unit area of canopy is equated with the estimates of evaporation derived from the Penman-Monteith equation there is an improved description of the observations.

Fitting the analytical model of rainfall interception of Gash to individual shrubs of semi-arid vegetation in northeastern México

This study was conducted to estimate the components of interception loss and to fit the analytical model of rainfall interception of Gash to a semi-arid plant community in northeastern México. The interception and components of interception loss were estimated from measurements of gross rainfall, throughfall and stemflow in individual shrubs of Diospyrus texana, Acacia farnesiana and Prosopis laevigata. The components of the interception loss did not deviate from other estimates in other ecosystems, except for evaporation rate during storms. In general, the analytical model performed well, although estimated total interception loss was highly sensitive to changes in both the magnitude of evaporation rate during storms and the proportion of rainfall that is stemflow.

An analytical model of rainfall interception by forests

The description of the evaporation of rainfall intercepted by forests in terms of a regression of evaporation loss on incident rainfall is discussed and some of the assumptions implicit in that method are re-examined. The two major factors which control the evaporation of intercepted rainfall are identified. These are: (i) the amount of time that the canopy spends saturated during rainfall and the evaporation rate applicable under these conditions; and (ii) the canopy saturation capacity and the number of times this store is emptied, by drying out after the cessation of rainfall. A model is then constructed which is conceptually similar to the Rutter model, but which replaces that model's numerical approach with an analysis by storm events. The evaporation from a saturated canopy during rainfall is estimated from the Penman-Monteith equation; the evaporation after rain has ceased, the effect of small storms insufficient to saturate the canopy, wetting-up the canopy and evaporation from the trunks are added as separate terms. The model has been tested against data from Thetford Forest in East Anglia, with satisfactory agreement between observation and estimation. It is suggested that the model may be capable of making useful estimates of the evaporation of intercepted rainfall, solely from rainfall measurements.

An analytical model of rainfall interception by forests

AbstractThe description of the evaporation of rainfall intercepted by forests in terms of a regression of evaporation loss on incident rainfall is discussed and some of the assumptions implicit in that method are re‐examined. The two major factors which control the evaporation of intercepted rainfall are identified. These are: (i) the amount of time that the canopy spends saturated during rainfall and the evaporation rate applicable under these conditions; and (ii) the canopy saturation capacity and the number of times this store is emptied, by drying out after the cessation of rainfall. A model is then constructed which is conceptually similar to the Rutter model, but which replaces that model's numerical approach with an analysis by storm events. The evaporation from a saturated canopy during rainfall is estimated from the Penman‐Monteith equation; the evaporation after rain has ceased, the effect of small storms insufficient to saturate the canopy, wetting‐up the canopy and evaporation from the trunks are added as separate terms. The model has been tested against data from Thetford Forest in East Anglia, with satisfactory agreement between observation and estimation. It is suggested that the model may be capable of making useful estimates of the evaporation of intercepted rainfall, solely from rainfall measurements.