How Rainfall Affects Ugum Watershed on Guam - Research Paper Example

How Rainfall affects Ugum Watershed on Guam The Ugum Watershed’s topography is 13.5 degrees at the northern part of the equator, thus found within the typical tropical climate, whose temperatures ranges fall between 70°F and 90°F. Therefore, this region receives a high level of rainfall owing to its location, hence it is the wettest part of the Uguam region at large. However, the high rainfall levels have been the cause of concern on how well the watershed management can be effected in order to prevent the continued depletion of the region’s soil nutrients due to frequent soil erosion. As a water source for numerous rivers in the region, there has been the aspect of the rivers originating here causing pollution of water in the eventual destinations. This study evaluated the different rainfall patterns for the area, together with how this impacts on the general regional geology. Several important physical properties are considered, including the vegetation cover of the area, topography, climatic conditions, and the effect of the rain on coral reefs. The study is particularly important since the findings are suited for application in enhancing soil conservation of the Ugum Watershed and the general Guam area. Table of Content Table of Contents Introduction 4 Methodology and Material 5 Field sampling and data collection 5 Results 7 Discussion 8 Conclusion 9 Brief History 10 Definition of terminologies 10 Physical Location 10 Socio-Economic Description 11 References 12 How Rainfall affects Ugum Watershed on Guam Introduction The Ugum Watershed’s topography is 13.5 degrees at the northern part of the equator, thus found within the typical tropical climate, whose temperatures ranges fall between 70°F and 90°F. Additionally, the region is dominated by easterly prevailing winds. As a region lying within the typhoon belt of the Western Pacific, Uguam is prone to severe rain and wind. For instance, the region averegely receives rainfall that ranges from 80 to 120 inches annually (Khosrowpanah & John, 2005). Ugum watershed lies in the Guam on the windward side and on the highest elevation of the area, thus becoming among the Guam’s wettest regions. Studies in the recent past have revealed a relatively complex pattern of rainfall distribution than previously reported, though still indicate that the area’s highest amount of rainfall annually is recorded within the Ugum watershed’s headlands. The Majority of the rains within the volcanic areas of the south Guam have a direct entry into the stream valley. This island is endowed with 100 streams that have variable lengths of between less than one kilometer to above five kilometers. These flows in V-shaped and deeply incised valleys within the highland areas, and in flat and wide-bottomed valleys of the coastal lowland, which are characterized by the intersection of water table and ground surface. These volcanic soils characteristically exhibit variable ranges of depth, but with good drainage. These soils are dominant in the mountainous terrains of the south, with most of them found within the steep settings. Similarly, the limestone soils are virtually shallow and with good drainage. These soils are largely present in the southern Guam parts with moderately sloped settings. The sand-line soils are characteristically deep with poor drainage, and are mostly found in the coastal plains and valley bottoms. Soils are an important component of healthy terrestrial ecosystem hence should be conserved. The Guan region is under pressure of handling the rapid urbanization process and the growing population, which largely depend on the productivity of the soils (Scheman, 2002). It is, however, evident that water pollution and soil erosion are among the critical hurdles the region has to overcome. Protection of the Guam watershed from the different sources of pollution, including the point and non-point has become a priority, and this has been greatly determined by the soil properties, vegetation, topography, information on land cover, badlands, and roads among other features. This study sought to determine the effect of rainfall on the Ugum Watershed on Guam, as an important feature for sustenance of the region. This is an important topic worth considering since the watershed is important to the general population in the region, and the information gained would be of great importance towards conservation of the features. Methodology and Material The research study was carried out in the Ugum watershed, which is the drainage basin for both Bubulao and Ugum rivers that form the Talofofo River’s major tributaries on the south. Three plots measuring 20 x 2.0 m each demarcated on the stretch of the watershed with uniform slope. In each of the plots, there was an excavation of soil profile representation to 80 cm deep in the surface of the soil, before the porosity, bulk density, retention capacity and field capacities of the plots were measured, in line with Van Remortel, Maichle and Hickey (2004) research method. Field sampling and data collection In line with each of the rainfall events, there was the collection of the soil samples and litter layers of the soil profile on a daily basis from between 8:00 and10:00 AM, for seven consecutive days between August and September 2006. The collected samples of the soil were then sectioned into respective 5cm and 10 cm quantity ranges (0–5, 5–10, 10–20, 20–30, 30–40, 40–50, 50–60, 60–70, and 70–80). The samples were eventually put in glass bottles and sealed using parafifilm, before they were temporarily stored in cooler at between 0 and 5oC (Tetra Tech & USEPA, 2006). This was then followed by the transfer of the same samples to the laboratory for refrigeration at 20oC prior to laboratory analysis. The analysis of soil texture of the sites was done at the beginning of the experiment, and the organic matter in the same determined. For the purposes of evaluating the effects of different rain patterns on the different soil texture, and eventual quantification of the turbidity and sedimentation of the runoff water of the respective plots, it was important to examine various treatments, which included: i. The state of natural vegetation and its treatment ii. The treatment of VS iii. The treatment of the exposed surface or tiled surfaces iv. The treatment of the controlled burn These aforementioned treatment practices and conditions or soil surfaces are representative of the variable ranges of conditions representing the typical south Guam area. Treatment with the natural conditions of native vegetation was done for the purpose of comparison (Van Remortel, Maichle & Hickey, 2004). The vegetation of the native plots was Savanna, and formed the major part of the xeric ecosystem that is characteristically dominated by low shrubs, scattered small trees and grasses, although there are some limestone and wetland species. Following every rain event, two tubes made from PVC were installed horizontally at downhill profile, at depths of 60 and 120 centimeters, then connected to the collection buckets. The water collected from the aforementioned soil depths was eventually mixed to constitute an interflow sample. The shallow samples of ground water were obtained from three wells with an approximate depth of 1.5 m prior to and after rain events (Donnegan, Butler, Hiserote & Limtiaco, 2004). These wells were formed naturally by a spring outlet on the ground closer to every one of the plots. At the time of rainfall events, there was the collection of eleven water samples on the open sites, approximately 100m far from the study region. All the rainwater, soil interflow, and the samples from shallow groundwater collection was done on every sampling day at around 8:00 AM. The samples of water were then put in plastic bottles before being sealed by use of parafilm. They were then put in a cooler at between 0 and 5oC prior to their refrigeration at 20oC in the laboratory, during which the hydrogen isotopes were analyzed, using an upper clean portion of each of the samples collected (Gazis & Feng, 2004). The data related to evaporation, precipitation, as well as the temperatures was then collected. Results At the time of study, variable rainfall events were recorded. On the other hand, the soil texture evaluated at the start of the experiment revealed that there were 24.9 % sand, 54.4% clay, and 20.7% silt, thus demonstrating that the soil was generally clay. In addition, the content of organic matter within the soil studied was recorded as averagely 3.9%. Recorded data indicated a significant correlation between the physical properties of the soil, but not for the three others that included the relationship between field capacity and non-capillary porosity, porosity between capillary and non- capillary, as well as the maximum capacity of retention and non-capillary porosity. There was the presence of rocks at depths ranging from 60 to 80 centimeters under the surface. It was also realized that vetiver system (VS) plots demonstrated lower levels of erosion compared to other plots during the rainy season, and this represented less than a third of that from plots with natural vegetation, and less than one percent that of plots with bare surface. On the other hand, the erosion of soil was highest following major events characterized by storms. It was also noted that the sedimentation amount was highest in the plots that lay bare on their surfaces than those that exhibited vegetations. Discussion The precipitation effects on the soilwater content is dependent on both intensity of rainfall and evaporation, in addition to infiltration. Heavy rainfall resulted in an increase in soil water content causing saturation of the surface layer of the soil, as well as increased content of soil water content within the upper layers. This means that heavy rainfall during summer, especially during El Nino, could result in the recharge of the groundwater, thus increasing streamflow (Lee, Kim, Lee, & Lee, 2007). Vetiver is among the most common plants considered important in the conservation of the ecosystem through erosion prevention. The plant is characterized by grass bunch that is significantly dense and stiff stems, in addition to the strong root system and long heights. The plant cannot produce seeds, hence does not result in weeds upon growth. Results reveal that mountainous and volcanic southern Guam is vulnerable to soil erosion during the rainy seasons (Huo, Zhang, Zhang & Zhang, 2009). As a result of severe soil erosion in the upstream in these seasons, there was common evidence of muddy fresh water entering the sea at the river mouth thus destroying the available coral reefs. The Guan region receives an average annual rain of 2,200 mm annually, with the majority experienced between June and November (Lander & Guard, 2003). The runoff water in the region characteristically occurs with high velocity flash floods, but last for a short period. The rapid water flow is as a result of low infiltration of the soil and the high amount of rains that is converted to overland flow. Within areas that have minimum protection cover and poor quality of soil, the soil experiences the sheer force of the overland flow compared to better protect lands. Ideally, it can be understood that through sediment deposition or soil removal and nutrient removal, there is an alteration of chemical and physical properties of the soil through erosion. The alteration leads to eventual degradation, thus impacting negatively on the environment and the entire process of ecosystem sustainability and productivity. The on-site damages caused by erosion are indeed a great problem in the environmental ecosystem, particularly in the south of the island (Khosrowpanah & Jocson, 2005). The sediments that are lost in the process of erosion result in clogging of lakes, rivers, and waterways, as well as reducing the storage capacity of water for the canals and reservoirs, hence increasing flooding. Therefore, sedimentation loss and erosion constitute the main source of the water-quality problems within the Guam region. Sedimentation is also found to have adverse effects on the coral reefs found near the shore in the ecosystem. The sedimentation resulting from terrestrial runoff constitutes the greatest anthropogenic threat to both Guam and other water resources in the Pacific Islands, as well as the ecosystem of the near shore coral reefs. Rainfall, among other non-point water sources results in significant pollution, thus posing a significant threat to the quality of near shore water and the coral reefs in general. Since sediments virtually bury the coral reefs, sedimentation is part of the causes of mortality during the early life stages of the hard corals, as observed by Rose (2004). Sediments may lead to reduced rates of recruitment and when at higher concentrations, affect the ranges of parameters of life history in adult and juvenile corals. In the previous decades, the increase in population as well as the evident changes in usage of land has resulted in a significant increase of the surface runoff, together with the associated water quality decline. This has in turn impacted the ecosystem of coral reefs hence threatening the coral reefs’ well being (Huo, Zhang, Zhang & Zhang, 2009). Conclusion Controlling soil erosion that is caused by intensive rainfall at times of high rainfall is a task that is important and challenging for the soil conservatists, scientists and foresters within the Guam area. The soil conservativists and soil scientists have the task of selecting, employing, and evaluating the vegetative systems that are effective in forming the dense hedge on the contours, and those with dense and strong leaves and stems that demonstrate a high level of resistance to flooding. Brief History A section of the southern Guam, which are under limestone cover, has a significant number of groundwater bodies, whereas the areas in which the limestone is under complete surrounding of volcanic terrains include the perched groundwater that is located in the permeable outcrops of limestone, and lie on the low-permeability volcanic rocks. This means the region is covered by soils with natural matter that is unconsolidated on the earth’s surface, with the main constituents being minerals, fragments, water, and organic matter. The conditions of the soil, amongst which are permeability, types, and the moisture have a great influence on the practices that can be undertaken on the land. Similarly, these conditions influence the habitat and potential of vegetation, as well as the overland runoff that results in landslides and erosion. Definition of terminologies Physical Location Geology- refers to the general study of the different aspects of the earth\s solid nature, together with their respective compositions. Topography- this is the practice involving detailed delineation of graphics on charts or maps of either natural or artificial features of a given region or place, particularly in a manner that portrays their location in relation to elevations and position. Climate- refers to average patterns of the different weather aspects within a given region over a long period of time. This involves observation of the different parameters and how there total impact on the region in the long run. El Niño –refers to the complex and irregular series of climatic changes that ultimately affect the regions of equatorial pacific. It characteristically exhibits unusual warmth, as well as water with poor nutrients. River- is a naturally occurring stream of water that flows within a channel with defined banks, leading it to a lake, sea, or other stream Soil- refers to the loose layer on the top of the earth’s surface, made up of mineral and rock particles in the mixture of humus. It provides nutrients and supports a variety of biotic communities, as well as retaining water. Erosion- the actions that accompany the exogenic processes of wind and water in the removal of rock and soil from a particular position on the earth’s surface to the other. Sediment- the fragmented solid material, including sand, slit, chemical precipitates, gravel of fossils, which are carried and deposited by wind, ice, or water, or accumulated through chemical precipitation. Coral reefs – these are adverse ecosystems beneath waters, which are held together by structures of calcium carbonate that are secreted by corals. Soil erosion effects- these are the physical, chemical, and economic outcomes that result from the soil erosion process. They are notably negative effects that deprive the earth surface of its nutrients hence compromising growth of plants on the surface. Socio-Economic Description Human population Demographic- this refers to the detailed description of people in a given setting, in relation to their ages, social status, gender, marital status, and other person-dependent features. Agriculture Land use- refers to the general practices done on the given piece of land by humans, with the aim of enhancing crop production and other practices that maximize food production. Food web- can be also be termed as consumer resource system. This portrays the existing link between different levels of feeding in a given ecological community. References Khosrowpanah, S., & John, J. (2005). Environmental Assessment for Non-Point Sources of Pollution for Ugum Watershed, Rep. No. 109, University of Guam Rose, C. (2004). An Introduction to the Environmental Physics of Soil, Water, and Watersheds Scheman, N. (2002). M.S. thesis on Identification of Erosion Process and Sources of Exposed Patches in the La Sa Fua Watershed of Southern Guam. WERI, University of Guam Van Remortel, R., Maichle, R., & Hickey, R. (2004). Computing the RUSLE LS Factor based on Array-based Slope Length Processing of Digital Elevation Data Using a C++ Executable. Computers and Geosciences, 30(9-10), 1043-1053. Lee, K,S., Kim, J,M., Lee, D,R., & Lee, D. (2007). Analysis of water movement through an unsaturated soil zone in Jeju Island, Korea using stable oxygen and hydrogen isotopes. Journal of Hydrology, 345: 199–211. Gazis, C., & Feng, X. (2004). A stable isotope study of soil water: evidence for mixing and preferential flow paths. Geoderma 119(1–2), 97–111. Huo, X, P, Zhang, J., Zhang, X, H., & Zhang, L, H. (2009). Soil permeability capability of subalpine coniferous forests in western Sichuan, China. Research of Soil and Water Conservation, 16: 192–195. Tetra Tech, Inc. & USEPA. (2006). Draft Sediment TMDL, Ugum Watershed, Guam USA. Donnegan, J,A.., Butler, S, L., Hiserote, B, A., & Limtiaco, D. (2004). Guam’s Forest Resources, 2002. Resour. Bull. PNW-RB-243. Portland, OR: US Department of Agriculture, Forest Service, Pacific Northwest Research Station GEPA. (2006). Integrated Report – September 2006. Clean Water Act, Sections 303(d), 305(b) and 314. Barrigada, GU: Guam Environmental Protection Agency. Khosrowpanah, S., & J, Jocson. (2005). Environmental Assessment for Non-Point Source of Pollution for Ugum Watershed, WERI Technical Report No. 109. Mangilao, Guam: University of Guam, Water and Environmental Research Institute of the Western Pacific Lander, M, A., & C.P. Guard. (2003). Creation of a 50-Year Rainfall Database, Annual Rainfall Climatology, and Annual Rainfall Distribution Map for Guam. WERI Technical Report No. 102. Mangilao, Guam: University of Guam, Water and Environmental Research Institute of the Western Pacific. Read More