Rainfall History Research Articles

The 2002–2003 El Niño recorded in Australian cave drip waters: Implications for reconstructing rainfall histories using stalagmites

A 30‐month study of drip hydrochemistry from Kooringa Cave, eastern Australia, revealed a clear geochemical response to the 2002–2003 El Niño. Through the drought, drip discharge fell to base flow, drip Ca2+ concentrations fell by half and drip Mg/Ca and Sr/Ca increased in a co‐varying pattern. Calcite Mg/Ca and Sr/Ca predicted from drip waters displayed a marked increase through, and just beyond, the period of greatest moisture deficit. The results suggest that stalagmites from shallow caves in drought‐sensitive eastern Australia potentially preserve a valuable record of El Niño‐La Niña history.

A 1500‐year El Niño/Southern Oscillation and rainfall history for the Isthmus of Panama from speleothem calcite

The effect of the El Niño/Southern Oscillation (ENSO) on tropical rainfall variations of the past 2 millennia is largely unknown. High‐resolution monsoon records are sparse, despite the role of ENSO in generating global hydrologic anomalies in modern climate. To investigate the relationship between ENSO and the Central American Monsoon, we generated a high‐resolution (∼2.9 years/sample) oxygen‐isotope monsoon rainfall record from a U/Th‐dated stalagmite (180 B.C. to 1310 A.D.) from the Isthmus of Panama. We present evidence for a weakened monsoon during the “High Medieval” (1100–1200 A.D.) and the Classic Maya Collapse (750–950 A.D.). Rainfall decreased and was more variable after 550 A.D., and the period 900–1310 A.D. was drier than the preceding millennium. A weaker monsoon corresponds with increased El Niño variability, and our data display statistical variance in the ENSO band. We conclude that ENSO variation has forced isthmian rainfall and may have contributed to hemispheric climatic anomalies at this time.

A robust rainfall‐runoff transfer model

This paper describes a simple and flexible new approach to rainfall‐runoff transfer modeling, which jointly models the mean and the variance structure of runoff. Its mean is taken to be a linear autoregressive combination of present and previous rainfall and previous runoff, while its variance also depends on rainfall history. Inference for our model is performed using classical likelihood methods, and also by the more robust technique of quasi‐likelihood, presupposing no particular distribution for runoff. The model has been developed on the Biorde catchment in Switzerland and calibrated and validated for 12 small Swiss catchments, with promising results.

Site-specific high-resolution models of the monsoon for Africa and Asia

Using the macrophysical climate model of Bryson [Bryson, R.A., 1992. A macrophysical model of the Holocene intertropical convergence and jetstream positions and rainfall for the Saharan region. Meteorol. Atmos. Phys., 47, pp. 247–258], it is possible to calculate the monthly latitude of the jetstream and the latitude of the subtropical anticyclones. From these and modern climatic data, it is possible to model the two-century mean latitude of the intertropical convergence (ITC) month by month and estimate the monthly monsoon rainfall using the ITC–Rainfall model of Ilesanmi [Ilesanmi, O.O., 1971. An empirical formulation of an ITD rainfall model for the tropics — a case study of Nigeria. J. Appl. Meteorol., 10, pp. 882–891] and similar relationships. Input to this model is only calculated radiation and atmospheric optical depth estimated from a database of global volcanicity. Recent work has shown that it is possible to extend these estimates to both precipitation and temperature at specific sites, even in mountainous terrain. Testing of the model against archaeological records and climatic proxies is now underway, as well as refining the fundamental model. Preliminary indications are that the timing of fluctuations in the local climate is very well modeled. Especially well matched are the modeled Nile flood based on calculated rainfall on the Blue and White Nile watersheds and the level of Lake Moeris [Hassan, F., 1985. Holocene lakes and prehistoric settlements of the Western Faiyum, Egypt. J. Archaeol. Res., 13, pp. 483–501]. Modeled precipitation histories for specific sites in China, Thailand, the Arabian Peninsula, and North Africa will be presented and contrasted with the simulated rainfall history of Mesopotamia.

Broad-scale environmental relations of floristic gradients in the Mitchell grasslands of Queensland

A large floristic data set was collated from vegetation surveys of Mitchell (Astrebla spp.) grasslands in Queensland spanning more than 20 years. The data was ordinated using non-metric multi-dimensional scaling and a four-dimensional solution could be deciphered. The longest floristic gradient was clearly aligned with climatic variables associated with mean annual precipitation. The vector for mean annual temperature was orientated orthogonally to the primary vector and was strongly correlated through the ordination space. A grazing vector tentatively derived from the frequency of species known to be favoured by grazing in Mitchell grasslands was orthogonal to the major climatic trends. However, the suspected grazing influence is complicated by the potential influence of sites occurring on limited areas of limestone habitat representing marginal Mitchell grassland habitat. A vector derived from the binomial categorisation of landform into downs and alluvia was clearly aligned with the fourth dimension of the ordination. Short- and long-term rainfall history variables were generated for each site from local rainfall records. The oblique trajectory of these variables through the ordination space tends to suggest that they may be artefacts of sampling rather than a major independent influence on the character of Mitchell grasslands. Thus the results at the broad scale of this study do not conform to previous studies at the paddock scale that emphasise the influence of climatic fluctuations on the floristic character of Mitchell grasslands. The results suggest Mitchell grasslands will require conservation planning and action throughout their geographic range.

Short-Term Variability of Water Quality Parameters in Two Shallow Estuaries of North Carolina

We quantified the effects of nutrient loading following precipitation events (≥ 1.25 cm) in 2 tidal creeks varying in size and anthropogenic input during the winter and summer seasons of 1996. Several water quality parameters were repeatedly measured in the water column every 3 h for several days after each event (4–5 per season). Total nitrogen (TN) and total phosphorus (TP) behaved nonconservatively with salinity and appeared as pulsed additions, occasionally doubling within 1 to 2 tidal cycles following significant rain events. Average values for TN, TP, and chlorophylla were 10–15 μM, 4 μM, and ≥ 7 μg l−1, respectively for summer events. However, response times were variable, depending on the magnitude and duration of the event as well as temperature. Chlorophylla biomass often increased after nutrient additions, especially in the summer when increased nutrient loading took place. Dissolved silica (DSi) behaved conservatively with salinity; low values were observed at high tide and vice versa. Average DSi ranges for winter and summer events were 5–45 μM and 10–85 μM, respectively. DSi range values increased proportionally with the amount of freshwater loaded into the system. Recovery times for salinity were usually greater than the recovery times for nutrients. Dissolved oxygen displayed a diel pattern, increasing after daytime productivity and decreasing during nighttime. In conclusion, each rainfall event was unique and responses were variable depending upon rainfall history, seasonality, and the duration and intensity of the rainfall event. Several other variables, such as water viscosity, percolation rates, and evapotranspiration rates which were not quantified in this study, could have also explained parameter responses.

Small Storm Hydrology and Why it is Important for the Design of Stormwater Control Practices

Different drainage design criteria and receiving water use objectives often require the examination of different types of rains for the design of urban drainage systems. These different (and often conflicting) objectives of a stormwater drainage system can be addressed by using distinct portions of the long-term rainfall record. Several historical examinations (including Heaney, et al. 1977) have also considered the need for the examination of a wide range of rain events for drainage design. However, the lack of efficient computer resources severely restricted long-term analyses in the past. Currently, computer resources are much more available and are capable of much more comprehensive investigations (Gregory and James 1996). In addition to having more efficient computational resources, it is also necessary to re-examine some of the fundamental urban hydrology modeling assumptions (Pitt 1987). Most of the urban hydrology methods currently used for drainage design have been successfully used for large “design” storms. Obviously, this approach (providing urban areas safe from excessive flooding and associated flood related damages) is the most critical objective of urban drainage. However, it is now possible (and legally required in many areas) to provide urban drainage systems that also minimizes other problems associated with urban stormwater. This broader set of urban drainage objectives requires a broader approach to drainage design, and the use of hydrology methods with different assumptions and simplifications. This paper reviews actual monitored rainfall and runoff distributions for Milwaukee, WI (data from Bannerman, et al. 1983), and examines long-term rainfall histories and predicted runoff from 24 locations throughout the U.S. The Milwaukee observations show that southeastern Wisconsin rainfall distributions can be divided into the following categories, with possible management approaches relevant for each category of rain: • Common rains having relatively low pollutant discharges are associated with rains less than about 0.5 in. (12 mm) in depth. These are key rains when runoff-associated water quality violations, such as for bacteria, are of concern. In most areas, runoff from these rains should be totally captured and either re-used for on-site beneficial uses or infiltrated in upland areas. For most areas, the runoff from these rains can be relatively easily removed from the surface drainage system.

Modelling the Effect of Seasonal Flow Variations on the Position of Salt Wedge in a Microtidal Estuary

The Swan River estuary, a microtidal estuary in the south-west of Western Australia, has a largely seasonal cycle of salinity variation due to the low tidal amplitude and strongly seasonal rainfall. In contrast, macro- and mesotidal estuaries may have semi-diurnal, diurnal or fortnightly periodicities in salinity variation. The temporal variation of the position of the salt wedge in the upper reaches of the Swan River estuary was analysed using field data and a laterally averaged, two-dimensional numerical simulation model for very dry (1993–94) and very wet (1973–74) years in the recent rainfall history. The salt wedge dynamics in the estuary are considered to have three phases; salt wedge dominated during summer and autumn characterized by very low freshwater discharge; salt wedge waning or absent in late winter and early spring with high flow; and salt wedge emplacement during late spring and early summer with low flow. During 1974, when the river inflow was greater than that of other years and remained substantial until early summer, the upstream salt wedge propagation during spring and early summer was strongly inhibited by river discharge. The correlation between the longitudinal location of the salt wedge and the inflow for 1994 (r2=0·86) further suggests that freshwater inflow is the most important mechanism affecting the salt wedge position in the Swan River estuary. When applied to other years this predictive tool gave reasonable predictions of the salt wedge position. The recorded positions of the salt wedge for the 4 years of study were compared against results of numerical model simulations, inflow correlations and the Hinwood formulation. Each method provided an adequate description of the salt wedge location apart from Hinwood's formulation for low river discharges, which greatly overpredicted upstream movement of the wedge.

Long‐term effects of daily grazing orbits on nutrient availability in Sahelian West Africa: 2. Effects of a phosphorus gradient on spatial patterns of annual grassland production

Abstract. This paper reports on an investigation of the effect of a livestock‐generated gradient in phosphorus‐availability on spatial patterns of annual rangeland production around pastoral watering points in the Sahelian region of West Africa. The study was conducted along a major transhumance corridor used for at least the past century by herds managed by agropastoralists of the Inland Niger Delta of Mali. Eighteen sites on sandy substrate were established at varying distances from: (1) a more persistent pan from which livestock disperse to graze primarily during the early dry season (D1); and (2) a line of ephemeral pans from which livestock disperse to graze during the rainy season (D2). Data on the species composition, standing herbaceous mass, and annual herbaceous cover were collected at these sites over the 2 years following a significant drought. These vegetative parameters show considerable interannual variation in their spatial pattern. As reported elsewhere (companion paper), chemical analyses of soil and plant samples collected at these sites show a significant negative correlation between phosphorus availability and D2. This is consistent with livestock‐mediated nutrient transfer from outlying zones toward rainy‐season pans. The effect of this phosphorus gradient on annual rangeland production was analysed using a regression modelling approach. Two vegetative production parameters, vegetated surface fraction (VSF) and herbaceous above‐ground standing mass of vegetated surface (VAGM), were regressed in a two‐and three‐step process on the following factors: (1) background soil and rainfall data; (2) forb fraction of herbaceous production (for VAGM only), followed by: (3) D1 and D2. These analyses find that while the phosphorus‐availability gradient had a significant effect on spatial patterns of herbaceous production during the year immediately following the drought, it had little effect in the subsequent year's production. This difference is explained by the increased importance of nitrogen in limiting herbaceous production during the second year, resulting from its different rainfall history.

The Effect of Environmental Variables on Capture Success of The Platypus Using Gill and Fyke Nets.

Capture success of platypuses using gill and fyke nets over the period 1986-1993 has been assessed against a range of environmental variables using the Spearman's Rank Correlation Coefficient and in some cases simple linear regression models. Approximately 90% of all animals captured during this study have been netted between 1730 hours and 0I00 hours regardless of age or sex. The peak capture period during which approximately 60% of animals were captured is between 1730 and 2230 hours. Variables examined included; number of platypuses captured, giII and fyke net hours, number of nets used, time nets set up and taken down, maximum and minimum day temperatures, time of sunrise and sunset, moon phase, time of moon rise and set, cloud cover, wind and rain conditions during trapping, 24 hour rainfall history prior to netting and some flow data. The number of nets, netting time, rainfall within 24 hours and temperature conditions all effect the chance of platypus capture in fyke nets (p<0.05). The number of gill nets and the time they are utilised are both positively correlated with platypus captures (p<0.05). However, there are differences between sexes and age groups. Using gill nets, platypuses are more likely to be captured during clear nights and less likely to be captured during summer months. The probability of trapping males, females, adults and juveniles varies with the seasons.

Using gravestones to assess changing rates of weathering in the United Kingdom

AbstractWeathering rates were calculated using the height difference between lead lettering and marble on gravestones at three sites in the UK. Comparison of their regression lines and residuals suggested that two of the sites, Portsmouth and Wolverhampton, had similar amounts and rates of weathering over the last 100‐150 years. Gravestones in Swansea appear to have weathered much more and much faster than gravestones at the other two sites. These differences may be the result of the differing pollution and rainfall histories of the three sites.

Recruitment Characteristics of the White Cypress Pine (Callitris Glaucophylla) in Arid South Australia.

Callitris glaucophylla is a long lived tree which has had limited spasmodic recruitment in the South Australian arid zone in recent years. Domestic stock and rabbit grazing have been implicated as major factors limiting its regeneration. Factors influencing the recruitment and death of C. glaucophylla in the Roxby Downs region were investigated. The survivorship of C. glaucophylla seedlings, which germinated following flooding rains in March 1989, was monitored at three rabbit densities, with and without the protection of tree guards. Despite above average rainfall in 1989, all the monitored seedlings succumbed to desiccation within 18 months of germination. Grazing by rabbits had no impact upon regeneration. In an analogous study, the height distributions of young established C. glaucophylla groves were measured and used to assign groves to cohorts representing past recruitment events. Rainfall history was compared with the estimated age of C. glaucophylla stands. Successful regeneration of C. glaucophylla in the Roxby Downs region was dependent on uncommon prolonged periods of above average rainfall. Most successful C. glaucophylla recruitment occurred in distinct groves on deep sand.

Book Reviews - 'Queensland's rainfall history - graphs of rainfall averages 18880-1988'. Jacqui Willcocks and Philip Young. Queensland Department of Primary Industries Information Series, 1991.

of the statistics of the rainfall received at 269 locations throughout Queensland over the last 90 - 100 years. It is printed on A4 bond paper from camera-ready copy and has a soft cover. The general layout is good with stations being listed in both alphabetical and latitudinal and longitudinal position. One page is allocated per station. A seven-page

Temperature and rainfall estimates for the past 40,000 years in equatorial Africa

THERE has been considerable debate about the magnitude of the decrease in temperature1,2 and the change in precipitation3 in the African tropics during the last glacial period. With the advent of fossil pollen studies in equatorial regions, it is now generally agreed that the temperature did decrease at this time in tropical regions4, but the magnitude of the temperature fluctuations and discrepancies between the continental5 and marine6 temperature records have yet to be resolved7. Here we present new quantitative estimates of temperature and precipitation using a multivariate analysis8 of pollen time-series data from peat deposits in Burundi for the past 40,000 years9. For the last glacial period, our estimate of a temperature decrease of 4 ± 2 °C is less than those (ranging from 5 to 8 °C) derived from snow-line and tree-line records5,7. Model simulations7 indicate that the snow-line and tree-line estimates (from high-elevation sites at ˜4,000 m above sea level) are incompatible with the marine temperature record. Our lower estimate from a site of intermediate elevation may help resolve the differences between these records. We also estimate that the mean annual rainfall decreased by 30% during the last glacial period, in agreement with the rainfall history inferred from lake level fluctuations10.

Analysis of Climate Effects on Performance of Unpaved Roads

The performance of unpaved roads is strongly dependent upon the moisture content within the roadway profile. Unfortunately, there are no analytical models currently available for quantitatively predicting the influence of depth and time-dependent moisture distribution upon this performance. Existing procedures rely on laboratory or field tests, or indirect empirical correlations, to define the strength characteristics of each roadway layer in terms of a single, generally conservative value intended to reflect worst-case climatic conditions. This paper presents a rational methodology for analyzing the effects of site-specific rainfall and evaporation history upon the performance of unpaved roads. The methodology consists of a predictive model for weather-induced, soil-moisture changes over time; relationships between soil moisture, compaction level, and strength for a variety of typical roadway soils; and a damage analysis model tailored to low-volume unpaved roads. The capabilities of the proposed methodology are demonstrated through a numerical example. Performance predictions from the proposed methodology are comparable to those from more conventional approaches.

A survey approach to evaluating the effects of management on semi-arid lands in New South Wales.

One hundred and ten paddocks were surveyed to give an overview of the effects of management burning, grazing by cattle, goats and sheep, and protection from livestock, on major vegetation types in the rangelands. A commercial paddock scale was used to complement information previously available on dietary preferences of livestock from a few, small research sites. In this dry period study, estimates of woody and herbaceous cover were not significantly different overall among paddocks subjected to the various kinds of management. However, herbaceous cover in protected or spelled paddocks was better than in the others. Also, no significant relationships were found between woody cover and herbaceous biomass in any treatment. Despite moderate sample sizes, high coefficients of variation occurred throughout the results. These were regarded as being a true reflection of the variability between paddocks in the rangeland. Underlying differences between management types may have been masked by the heterogeneity of the paddocks within each type due to a complex history of rainfall, burning and grazing. Cluster analysis of the 110 paddocks revealed floristic (woody spp.) similarities of mulga, poplar-box, pine and some belah-rosewood woodlands, whereas saltbush and mallee were distinct. Further comparisons of management types were made on mulga woodland alone. Domestic goats were kept in the most heavily wooded paddocks and, in contrast with sheep, checked the growth of woody plants < 2m high. Woody growth recovered in the < 2m stratum several years after burning. Further evaluation of the herbaceous layer and of woody/herbaceous relationships is recommended after a wet summer.

A Method to Estimate the Probability that Subsoiling will Increase Crop Yields1

AbstractCrop yield responses to subsoiling are determined by the amount and distribution of rainfall and soil properties. Because growing season rainfalls are not known in advance, the likelihood of subsoiling increasing yields at a given site can only be stated in terms of probabilities based on current soil properties and historic rainfall patterns. In this study, the probability that subsoiling would increase tobacco (Nicotiana tabacum L.) yield as compared to a nonsubsoiled treatment was estimated for 20 coarse‐textured soils in the southeastern USA where significant yield increases from subsoiling had been observed previously or were expected. Using data collected from 1981 through 1984 for yields of subsoiled and nonsubsoiled treatments, soil physical properties, and rainfall from the 20 sites, a regression model was first developed to describe yield differences between treatments on the basis of specific weekly rainfalls and the sand percentage and water retention of selected horizons. The regression model was then used to estimate yield differences between treatments using physical properties of each of the 20 sites and rainfall histories of two Coastal Plain locations for the years 1930 through 1986. For each rainfall history, the number of years that the estimated yield differences between treatments were ⩾300 kg ha 1(significant differences in yields at the 0.05 level) was tabulated for each site and divided by 57 to compute the proportion of years that subsoiling would have significantly increased yields in the soils considered. These proportions were assumed to be the probabilities that subsoiling would increase yields for a given rainfall history and set of soil properties. The estimated probability mean and standard deviation were 0.69 ± 0.12 across all 20 sites and both rainfall histories. This indicated that on the average, subsoiling would be expected to increase tobacco yield in approximately 7 out of every 10 yr. Probabilities were < 0.50 in only two sites that had relatively high water retention values. The probability values decreased as E‐B horizon water retention increased and Ap horizon sand percentage decreased. These results pertain to Costal Plain soils that had bulk densities ⩾ 1.63 Mg m−3 in either the Ap or E‐B horizon, and sand percentages ⩾ 73% in the Ap horizon.

Recharge characteristics of an unconfined aquifer from the rainfall-water table relationship

The determination of recharge levels of unconfined aquifers, recharged entirely by rainfall, is done by developing a model for the aquifer that estimates the water-table levels from the history of rainfall observations and past water-table levels. In the present analysis, the model parameters that influence the recharge were not only assumed to be time dependent but also to have varying dependence rates for various parameters. Such a model is solved by the use of a recursive least-squares method. The variable-rate parameter variation is incorporated using a random walk model. From the field tests conducted at Tomago Sandbeds, Newcastle, Australia, it was observed that the assumption of variable rates of time dependency of recharge parameters produced better estimates of water-table levels compared to that with constant-recharge parameters. It was observed that considerable recharge due to rainfall occurred on the very same day of rainfall. The increase in water-table level was insignificant for subsequent days of rainfall. The level of recharge very much depends upon the intensity and history of rainfall. Isolated rainfalls, even of the order of 25 mm day −1, had no significant effect on the water-table levels.

Leaching of a sorbed solute: A model for peak concentration displacement

An investigation of the downward transport of a solute following a series of alternating irrigation/rainfall and evapotranspiration events is carried out. The principle of conservation of mass, and the concepts of partition chromatography are used in constructing a simple model which enables the peak solute concentration depth to be calculated at any particular time given the rainfall and evapotranspiration history. Prediction of the theory is compared with published data on solute transport.

A SEASONAL STUDY OF OXYGEN UPTAKE OF SOME PASTURE SOILS AND ACTIVITIES OF ENZYMES HYDROLYSING SUCROSE AND STARCH

SummaryRates of oxygen uptake and activities of enzymes hydrolysing sucrose and starch were determined in soils under pastures of grasses and clovers at bimonthly intervals at eight sites in New Zealand with different climates. Differences between sampling periods were significant in most soils. Values of oxygen uptake and enzyme activities were not generally significantly correlated between themselves nor with the moisture contents of the soils nor their prior rainfall history. It has not been possible to suggest an optimal sampling period for different soils. The oxygen uptakes of all soils increased two‐ to threefold in the presence of glucose. Mean annual values of oxygen uptake of the eight soils were significantly correlated with their contents of organic carbon, reducing sugars produced on incubation in buffer, and rates of hydrolysis of starch, but not of sucrose. Climatic factors and the composition of the pastures probably influence the activities of carbohydrase enzymes in soil. The ratios of the activities of enzymes hydrolysing sucrose to those hydrolysing starch were greatest in the driest soils under predominantly grass pastures at sites with the lowest mean annual temperatures.