Low-rainfall

This represents not only a loss of an essential nutrient for plant growth, but the ammonia is capable of generating alkalinity in rainfall (8). Because of the low rainfall in arid regions, this ammonia is likely to be transported for long distances before affecting the pH of the rainfall (8). 

Table 2 Fate and effects of metals in a stream receiving a point-source of metals (upper part of the table) or diffuse input via urban runoff (lower part of the table). Summary of the expected influence of four different hydrological situations base-flow in a rainy period a flood after a rainy period low-flow after a long period of low rainfall (water scarcity) and a flood produced after this drought. Metal concentration (M) metal retention efficiency (measured on the basis of the nutrient spiraling concept) exposure (dose and duration) bioaccumulation (in fluvial biofilms) and metal sensitivity (of biofihns)...

Very little evidence associating water scarcity and an increase in outbreaks of faecal-oral water-borne infectious diseases exists in developed countries. A recent retrospective study performed in England provides some evidence that both low rainfall and heavy rain precede many drinking water outbreaks [3]. Yet, as stated earlier in this review, the situation is potentially different in developing countries [5-7, 9-12], where water scarcity, including droughts, leads to different circumstances that have a clear incidence in the occurrence of both water-borne and water-washed infectious diseases. 

Craufurd, P.Q., Clipson, N.J., Austin, R.B. Acevedo, E. (1988). An approach to defining an ideotype for barley in low-rainfall Mediterranean environments. In... 

Because of the low rainfall and high evaporation rate, other water sources which might carry contamination Into the ground water were Investigated. The Company was required to check the Industrial water settling basin and all existing storm and sanitary sewers In the potllner area for leaks. 

The pH of Soils. The pH of soils (see Textbox 48) varies widely with location and climate the local climate of a region usually provides a clue as to the pH of the soil. In high-rainfall regions, for example, soils are generally acid. Alkaline soils, in contrast, typically occur in low-rainfall areas the actual value of the pH varies over a wide range, from below 5 in very acid... 

Because an assessment of this detail can be very difficult and costly to perform, however, (especially if it requires the use of complex fate models), exposure estimates may be limited to average seasonal conditions (e.g., summer — low flow — low rainfall, etc.) and to specific "worst case" meteorological or hydrological conditions for that area (e.g., inversion conditions, 7 day-10 year low flow). 

Field studies have shown that the first 5-6 mm of rain falling on a heated desert surface evaporate almost immediately, whilst single storms with more than 20 mm rain lose a major part of it by lateral runoff. Hence, it is estimated that from the already low rainfall in the arid zone an important part is lost for weathering and soil formation. The importance of this runoff... 

Seed quality depends heavily on the climatic characteristics of site locations. Thus, in order to limit seedbome disease inocula, seed production should be in areas characterized by low rainfall during flowering and ripening stages and by soils with low soil-nitrogen levels. 

Horizon Development under Low-Rainfall and Desert Conditions 32... 

Horizon Development in Areas between High- and Low-Rainfall... 

Under low-rainfall and desert conditions, the lack of rainfall results in very different soil conditions. Figure 2.6 shows the profile description of an Aridisol (an arid, desert, region soil) (see Section 2.4 for the explanation of the naming system). All lower horizons contain a high content of sodium ions and most also contain other soluble salts of various kinds. 

In low-rainfall regions, salts are not readily washed out of soils and may even build up on the soil surface. This happens when rain dissolves salts in the soil surface and leaches them a little way into the soil. Subsequent evaporation of water from the soil surface causes water and dissolved salts to move to and be deposited on the soil surface. No salts or only the most soluble salts are leached out of the soil, in low-rainfall regions, and the pH is typically basic. 

In areas between high and low rainfalls, horizonation may be well or poorly developed, soil pH may be either acidic or basic, and there may or may not be... 

Simple anions in soil are the halogens, chlorine (Cl ), and bromine (Br ). If present, the other halogens—fluoride, F, and iodide, I-—will also occur as simple anions. Because the compounds of these anions are generally soluble, they readily leach out of the soil and so are present at low concentrations. Exceptions occur in low-rainfall regions where significant, sometimes deleterious (to plants and animals), levels of simple anions can be found. 

The alkali and alkaline earth metals are examples of relatively simple cations that occur in only one oxidation state and are surrounded by water (see Figure 6.1). The most common of these ions in soil, in order of decreasing abundance, are calcium (Ca2+), magnesium (Mg2+), potassium (K+), and sodium (Na+). Sodium is typically present in very small amounts in high-rainfall areas, whereas it may have a relatively high concentration in low-rainfall areas. 

One place where soil solution from saturated soils is routinely used is in the determination of salts in soil. Salts can build up in soil in low-rainfall areas. A measure of the salt content is essential for these soils. Typically, a saturated paste of soil is made and the water filtered by vacuum filtration. The filtrate can then be analyzed for electrical conductivity and this measurement, together with calcium, magnesium, and sodium content, can be used to calculate various measures of salt content and potential detrimental effects of salts on crops and water quality. 

The feasibility of an evaporation pond is determined by the volume of concentrate, the cost of land and the ambient evaporation rate. They are most cost-effective in areas with low rainfall, high evaporation rates, and where large expanses of land are available at low cost (Mickley 2009). This best suits inland desalination plants in regional and remote areas where these conditions can be met. 

C1 activities measured near Richland resulted from some other cause than a low rainfall rate, such as a higher rain formation altitude. 

While not generally supported by researchers and producers at the time, attempts to find alternatives to moldboard plowing did produce some new implements, including the one-way disk plow. However, the one-way disk plow along with high temperatures and low rainfall were the primary causes of the Dust Bowl in the Great Plains. 

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