Percentage Of Annual Precipitation Research Articles

STUDY OF THE DISTRIBUTION OF PRECIPITATION IN DISTRICT OF EASTERN MACEDONIA AND THRACE FOR THE PERIOD 1964 -1998

This paper refers to the distribution and the quantitative approach of the precipitation of the Region of Eastern Macedonia and Thrace for the period 1964 - 1998 and it is based on data from 64 meteorological stations. The distribution of the precipitation varies significantly according to each different location. The mountainous terrain plays a significant role on the distribution of precipitation while the low height of precipitation is easily observed within the coastal zone. The dense forested areas are characterized by high precipitation heights and flood events. The mean precipitation for the period 1964-1998 is 660 mm. The elaboration of the rainfall data shows a distinct reduction during 1964-1998 with a drought period between 1981 and 1993. December and November are found to be the most wet months, while it is observed that 70.2% of the precipitation occurs between October and March. It is estimated that 76% to 80% of the precipitation are lower than 10 mm. The percentage of annual precipitation which outflows and/or infiltrates ranges between 23.5% to 42.5%.

Green roof performance potential in cold and wet regions

Extensive green roofs have become a frequently used option for stormwater retention across many different climates including cold and wet regions. Despite the extensive documentation of green roof technology for stormwater management, the knowledge about their function and potential use in wet and cold regions is deficient. Using historic data on daily temperature and precipitation in a green roof water balance model coupled with the Oudin model of evapotranspiration (ET), we evaluated the effects of maximum green roof storage capacities (Smax) and ET on stormwater retention along climatic gradients in Northern Europe. Large differences in potential annual stormwater retention were found between locations, driven by differences in temperature and precipitation amounts. Highest retention in absolute values was found for the wettest locations, while the warmest and driest locations showed highest retention in percentage of annual precipitation (up to 58% compared to 17% for the lower range). All locations showed a considerable retention of stormwater during summer, ranging from 52% to 91%. Storage capacities accepting drought conditions once every 3.3–3.9year were found to be about 25mm in the cold and wet locations increasing to 40–50mm in the warmer and drier locations. Corresponding storage capacities to prevent wilting of non-succulent vegetation was on average a factor of 1.5 larger (not including Sheffield and Malmö). Annual retention increased both with an increase in plant water use (specific crop factors, Kc) and with an increase in Smax, but was found to be more sensitive to changes in Kc than to changes in Smax. Hence, ET was the limiting factor for green roof retention capacity in the cold and wet locations, but relatively large changes in evapotranspiration would be needed to have an impact on retention. The potential to use vegetation with higher water use to better restore the storage capacity between storm-events in these regions was however limited by the risk of permanent wilting of non-succulent vegetation, even on the wettest locations. A considerable increase in roof storage capacity and substrate thickness would be required to reduce this risk; still the increase in stormwater retention would be marginal.

Infiltration in layered loessial deposits: Revised numerical simulations and recharge assessment

Summary The objective of this study is to assess recharge rates and their timing under layered loessial deposits at the edge of arid zones. Particularly, this study is focused on the case of the coastal plain of Israel and Gaza. First, results of a large-scale field infiltration test were used to calibrate the van Genuchten parameters of hydraulic properties of the loessial sediments using HYDRUS (2D/3D). Second, optimized soil hydraulic parameters were used by HYDRUS-1D to simulate the water balance of the sandy-loess sediments during a 25-year period (1990–2015) for three environmental conditions: bare soil, and soil with both sparse and dense natural vegetation. The best inverse parameter optimization run fitted the infiltration test data with the RMSE of 0.27 d (with respect to a moisture front arrival) and R 2 of 96%. The calibrated model indicates that hydraulic conductivities of the two soil horizons, namely sandy loam and sandy clay loam, are 81 cm/d and 17.5 cm/d, respectively. These values are significantly lower than those previously reported, based on numerical simulations, for the same site. HYDRUS-1D simulation of natural recharge under bare soil resulted in recharge estimates (to the aquifer) in the range of 21–93 mm/yr, with an average recharge of 63 mm/yr. Annual precipitation in the same period varied between 100 and 300 mm/yr, with an average of 185 mm/yr. For semi-stabilized dunes, with 26% of the soil surface covered by local shrub ( Artemisia monosperma ), the mean annual recharge was 28 mm. For the stabilized landscape, with as much as 50% vegetation coverage, it was only 2–3 mm/yr. In other words, loessial sediments can either be a source of significant recharge, or of no recharge at all, depending on the degree of vegetative cover. Additionally, the time lag between specific rainy seasons and corresponding recharge events at a depth of 22 m, increased from 2.5 to 5 years, and to about 20 years, respectively, with an increasing vegetative cover. For this reason, and also likely due to a great depth of loessial sediments, no correlation was found between annual recharge and annual precipitations of the same year or subsequent years. Similarly, no differences were found between summer and winter recharge fluxes. Instead, numerical simulations indicated continuous year-round recharge of the aquifer. We conclude that the layered subsurface acts as a short-term (annual) and long-term (multi-annual) buffer to smooth sudden precipitation/infiltration events. Vegetation conditions can help in predicting long-term recharge rates (as percentage of annual precipitation), which in turn need to be considered when assigning recharge characteristics in regional assessments and models.

Unsaturated water flux at mid and lower slope positions within an inclined landscape of the Dark Brown soil zone in southern Alberta

Miller, J. J. and Chanasyk, A. S. 2015. Unsaturated water flux at mid and lower slope positions within an inclined landscape of the Dark Brown soil zone in southern Alberta. Can. J. Soil Sci. 95: 27–36. Little research has quantified vertical-unsaturated water flux below the root zone for mid and lower slope positions within inclined, low-relief, and longer-slope landscapes of the Dark Brown soil zone of the Canadian prairies. We measured soil moisture (0.23–1.22 m) in the field at mid and lower slope positions in southern Alberta from May to October in 1985 and 1986. Undisturbed soil cores were taken from soil horizons and saturated hydraulic conductivity and soil moisture retention were determined in the laboratory. Vertical-unsaturated water flux below the root zone was calculated between 1.07 and 1.22 m depths below ground surface using the hydraulic gradient method. Water fluxes for the 2 yr ranged from <10−11 to 10−10 m s−1 at the mid slope position, and from <10−11 m s−1 to 10−9 m s−1 at the lower slope position, and were consistent with some other studies. Cumulative water flux was dominantly downward (−2.2 to −3.4 mm) at the mid slope position and this flow direction was consistent with this Orthic Dark Brown Chernozemic soil that was located in a “recharge area”. Cumulative water flux was dominantly upward at the lower slope position in 1985 (1.4 mm) and dominantly downward but of very low magnitude in 1986 (−0.1 mm), and this flow direction was consistent with this saline Gleyed Regosol and “saline seep”. Cumulative water fluxes as a percentage of annual precipitation were 0.8 to 1.8% at the mid slope position and 0.3 to 0.5% at the lower slope position.

Trends in the Output of First-order Basins at Turkey Lakes Watershed, 1982-96

In 1981, we began to monitor the stream flow and chemistry of 13 first-order basins at the Turkey Lakes Watershed, with the objective of measuring the response of an undisturbed forested ecosystem to acid deposition. There was no trend in total annual precipitation received by the watershed, but the average annual water yield (percentage of annual precipitation) declined over the observation period. The proportion of runoff occurring in different seasons also changed, decreasing in the winter and increasing in the spring. In most streams the concentration of SO4 2− has decreased coincident with the decline in precipitation inputs. Recovery of the basins from acid deposition (as evidenced by increased pH, increased alkalinity, and decreasing base cation fluxes) has not been uniform. Basins that do not show signs of recovery are characterized by deeper flowpaths and greater potential neutralizing capacity, which minimizes the impacts of acid deposition. Basins that are dominated by shallow flowpaths and lower levels of potential neutralizing capacity are showing some signs of recovery, but their recovery is not complete and it is possible that cation depletion may prevent or retard it.

Mineralogical composition of African dust delivered by red rains over northeastern Spain

The African dust deposition, mineralogy, source regions, and influence on rain chemistry were analyzed for a site in the Montseny mountains (Catalonia, northeastern Spain) for the period August 1, 1983, through August 1, 1994. Dust deposition was highly variable: two events (collected on November 9–11, 1984, and March 22–25, 1991) accounted for 62% of the total dust input in the 38 red rain events recorded in the period. The average annual dust deposition was 5.3 g m−2 (SE 2.6). Three source regions in the African continent were identified with back trajectory analysis: (1) Western Sahara, (2) Moroccan Atlas, and (3) Central Algeria. Events from the Moroccan Atlas predominated in terms of number of events, amount of rainfall, and dust deposition. The meteorological situations during red rains were identified: Western Sahara events occurred principally with a depression at high latitudes (50°N) forming a trough in the North Atlantic, Moroccan Atlas events occurred with a depression in front of Portugal, and events from central Algeria were associated with a depression over Spain or North Africa. By order of abundance (median of n=13) the minerals identified in the dust by X ray diffraction were as follows: illite > quartz > smectite > palygorskite > kaolinite > calcite > dolomite > feldspars. Differences in mineralogy between source regions were significant for smectite, kaolinite, quartz, and dolomite. Smectite and kaolinite content was highest in the Algerian events, while quartz and dolomite content was lowest. Events from the Moroccan Atlas had the lowest smectite and kaolinite. The red rain soluble chemistry was clearly influenced by the dissolution of calcite (high alkalinity, calcium concentration and basic pH) and by marine components (high Na+, Cl− arid Mg+2 concentrations). Because of the very alkaline character of red rains they had a strong weight on the annual mean pH of rainwater. This was reflected by the significant relationship (r=0.71, p<0.01) between the percentage of annual precipitation as red rain and annual mean precipitation pH. Red rains provided 25–45% of the annual dissolved input of the major ions in precipitation and 34% of the calcium required for holm oak (Quercus ilex L.) forest growth at the study site.

Quality and Quantity of Sanitary Landfill Leachate

This paper presents the results of leachate quantity and quality measurement at 20 landfills in the northern part of West Germany over an average period of 3 years. The leachate flow rate could only be estimated as a percentage of annual precipitation (measured precipitation 501-1057 mm year-1). The values for compaction with crawler tractors are 25-50% and with steel wheel compactors, 15-25%. The organic contents of leachate are dependent upon the kind of decomposition conditions (aerobic, anaerobic acetic production or anaerobic methane production). With anaerobic acetic production the volatile fatty acids produced in leachate have a high COD and BOD5. In the following methane production phase these acids are converted to CO2 and CH4 with low organic leachate contents. The concentrations of some inorganic components, such as Fe and Ca, are parallel as a result of changes in pH. Ammonia shows a slow increase with landfill age. In most cases the contents of heavy metals are lower than 1 mg 1-1.

Quality and quantity of sanitary landfill leachate

This paper presents the results of leachate quantity and quality measurement at 20 landfills in the northern part of West Germany over an average period of 3 years. The leachate flow rate could only be estimated as a percentage of annual pre-cipitation (measured precipitation 501–1057 mm year −1). The values for compaction with crawler tractors are 25–50% and with steel wheel compactors, 15–25%. The organic contents of leachate are dependent upon the kind of decomposition conditions (aerobic, anaerobic acetic production or anaerobic methane production). With anaerobic acetic production the volatile fatty acids produced in leachate have a high COD and BOD 5. In the following methane production phase these acids are converted to CO 2 and CH 4 with low organic leachate contents. The concentrations of some inorganic components, such as Fe and Ca, are parallel as a result of changes in pH. Ammonia shows a slow increase with landfill age. In most cases the contents of heavy metals are lower than 1 mg 1 −1.