Soil Erosion under Land Use Change from Three Catchments in Laos, Thailand and Vietnam

Abstract: The systems often identified as "traditional" undergo rapid changes as a response to demographic, economic, political and cultural drivers. These transitional periods are often most critical for soil erosion. The on-site impacts of soil erosion reduce the soil chemical fertility through nutrient and organic depletion, and acid subsoil exposure. Erosion also damages the physical fertility by removing surface soil, reducing the soil depth and water holding capacity, and exposing gravel and rocks. These combined processes result in less productive soils, hence lower farm income. To obtain the initial crop yield prior to erosion, increased amounts of inputs are needed, which is most often beyond the economic capacity of the small holders. To study the impact of land use change upon erosion, concurrent case studies, as seen with a dynamic perspective, can compensate for long-term monitoring studies. This approach provides data, which can be used for prediction soil erosion based on global change scenarios. The main objective of this study was to assess the influence of the rapid change of cropping systems on water erosion from three small catchments in three countries of South-East Asia (Laos, Thailand, Vietnam), using a multidisciplinary approach. These three catchments were selected because of their similar biophysical components (very steep slopes on shales; Janeau et al., submitted) and their land use intensification gradient. This investigation was conducted under the auspices the Management of Soil Erosion Consortium (MSEC) started in 1998 (Amado et al., 2002). Water discharge and soil erosion were monitored during three years at the outlet of each catchment using weirs. These data were used to calibrate and validate the PCARES model (Predicting Catchment Runoff and Soil Erosion for Sustainability) in each cachment. This GISbased model was developed in the Philippines for very steep slope condition

Tetracycline: production, waste treatment and environmental impact assessment

The frequent occurrence of pharmaceuticals in the aquatic environment requires an assessment of their environmental impact and their negative effects in humans. Among the drugs with high harmful potential to the environment are the antibiotics that reach the environment not only, as may be expected, through the effluents from chemical and pharmaceutical industries, but mainly through the sewage and livestock; because around 25 to 75% of the ingested drugs are excreted in unchanged form after the passage through the Gastro-Intestinal Tract. Tetracycline has high world consumption, representing a human consumption of about 23 kg/day in Brazil in 2007. At the moment, researches are being made to develop new tetracycline that incorporate heavy metals (Hg, Cd, Re, Pt, Pd) to their structures in order to increase their bactericidal effect. The conventional wastewater treatment plants are not able to degrade complex organic molecules to reduce their toxicity and improve their biodegradability. For this reason new technologies, i.e., the advanced oxidation processes, are being developed to handle this demand. The objectives of this study are to review the literature on the processes of obtaining tetracycline, presenting its waste treatment methods and evaluation of their environmental impact

Vetiver Grass: a Natural Barrier to Protect Against Organophosphate Pesticides from Cabbage Fields

ABSTRACT The absorption of organophosphate pesticides by cabbage and vetiver grass (Vetiveria zizanioides Nash.) was investigated at Khunkong Watershed Research Station, Chiang Mai, between January and May 2003. The experimental plots with 12 cabbages per square meter and rows of vetiver grass about 0.5 m down slope below the plots were established on an area of about 30% slope. Two samples per plot of cabbage, vetiver grass and soil, were collected, twice a month at 15 days after application and at one day before next application, except the first collection, which was carried out right after the initial spray. Except methamidophos, the results showed that all the test compounds accumulated in cabbage, which was not found in any samples because of its low persistence. The investigation of test compounds in cabbage during the 139 day experiment showed that the average uptake rate was ethoprophos (0.78 mg/g lipid weight.day) < methyl-parathion (0.93 mg/g lipid weight.day) < methidathion (1.86 mg/g lipid weight.day) < EPN (7.7 mg/g lipid weight.day) and the concentration factor (CF = C B / C S , g organic carbon /g lipid weight) order was similar as ethoprophos (log CF = 0.54) was < methidathion (log CF = 0.98 ) < methyl-parathion (log CF = 1.18) < EPN (log CF = 2.17). The concentration factors of the test compounds were highly related to their hydrophobicity (log K ow ) by log CF = 1.0696 log K ow -2.2347, r 2 = 0.87. In vetiver grass, only EPN was found in root samples with the absorbed concentration increasing with exposure time and in soil, EPN was the only compound which was found only in samples collected from the areas above vetiver grass rows. This result indicated that vetiver grass might be used to absorb organophosphate pesticides applied in agricultural areas

Statistical analysis of long-term series rainfall data: a regional study in Southeast Asia

In Maglinao, Amado R.; Valentin, Christian; Penning de Vries, Frits (Eds.), From soil research to land and water management: Harmonizing people and nature ? Proceedings of the IWMI-ADB Project Annual Meeting and 7th MSEC Assembly. Bangkok, Thailand: IWM

Statistical analysis of long series rainfall data: A regional study in Southeast Asia

In IWMI SOUTHEAST ASIA, KU ? IWMI Seminar on Scientific Cooperation, Kamphol Adulavidhaya Conference Room, Kasetsart University, Bangkok, Thailand, 26 March 200

Water balance of an australian subtropical rainforest at altitude: The ecological and physiological significance of intercepted cloud and fog

A water balance study of a small subtropical rainforest catchment (10 ha, 1000 m altitude) was conducted at Gambubal State Forest, near the headwaters of the Condamine River, 200 km south-west of Brisbane, south-eastern Queensland. Mean annual rainfall of the site is approximately 1125 mm, but is variable and often less than 900 min. Tree transpiration rates are low and depletion of the large soil moisture reserves enables extraction for lengthy periods of time, permitting survival during extended dry seasons (May-November). Fog deposition to the forest provides the equivalent of an additional 40% of rainfall to the site as measured using a conventional rain gauge. A frequently wet canopy results in reduced transpiration rates and direct foliar absorption of moisture alleviates water deficits of the upper crown leaves and branches during the dry season. These features of this vegetation type may enable long-term survival at what could be considered to be a marginal rainforest site

Potential and limitations of Payments for Environmental Services (PES) as a means to manage watershed services in mainland Southeast Asia

Based on two case studies conducted at local sites in Northern Thailand and Lao PDR, the objectives of this paper are (i) to assess whether conditions for the establishment of PES at the watershed level exist in the uplands of mainland SE Asia and (ii) to examine and discuss limitations that are likely to impinge on direct transfer of the PES concept as well as the institutional adaptations and support that are required for the successful implementation of PES markets in this regional context. The study's main findings are that: (i) acceptance of PES principles and constraints are directly related to stakeholders' perception of their land rights irrespective of their actual rights; (ii) willingness to pay (WTP) is very low among local stakeholders, making any PES market unlikely to emerge without external support; (iii) the classical scheme for watershed services hardly applies in its original form because environmental service (ES) providers and buyers are generally the same people; (iv) where potential ES buyers feel that ES providers are better-off or wealthier than them, they do not have any WTP for ES; (v) good governance, including a strong liaising at various levels between people and the authorities is a strong prerequisite for the successful establishment of PES markets, even without direct government fundin