Phreatic Depth Research Articles

Determination risk of liquifaction disaster based on spatial distribution unconfined aquifer at the Tindaki Groundwater Basin, Parigi Moutong District

Natural disasters such as earthquake, tsunami and liquefaction in Central Sulawesi Province in 2018 had a significant impact on economic growth. This demands disaster risk reduction, especially liquefaction disasters. This research was conducted in Tindaki Groundwater Basin, Parigi Moutong Regency, especially in Parigi sub-district, which includes: Lebo, Bambalemo, Kampal, Maesa, Bantaya, and Olaya. The purpose of this study was to determine the level of risk of liquefaction based on the spatial distribution of the unconfined aquifer in Tindaki Groundwater Basin. The number of samples is 100 points taken randomly, consisting of community dug wells to obtain phreatic depth. The technique of collecting data is random and proportional sampling.The method used in this study is geological and hydrogeological approaches with rock formation as a determining parameter for groundwater density. The results showed that the average depth of the phreatic level was <10 meters from the ground and was in the alluvium formation. Based on the results of the study, it can be concluded that the potential for liquefaction in the research area is in the medium to high potency.

Detection of Flood Inundation in the Progo Watershed using the SHETRAN Model

Floods are the most frequent disasters in Indonesia in the past 20 years. Based on the Indonesian Disaster Information Data (DIBI) compiled by BNPB, there are considered to be 9053 events (37.5%) of the total natural disaster events in Indonesia. The flood disaster has threatened and disrupted people’s lives and even resulted in fatalities, environmental damage, property losses, and psychological impacts. Therefore several efforts of flood risk reduction are required. One of them is to develop a model to detect the depth of flood inundation. The purpose of this study is to apply the SHETRAN Model for flood inundation detection in the Progo Watershed. The SHETRAN model is a distributed hydrological model. The data required in this model are hydro-climatological data, including rainfall and evaporation, land use land cover, soil type, and topography data obtained from remote sensing. The results of this study indicate that in the range from 2001 to 2017, the maximum height of flood inundation between the data on flood events in the field and the phreatic depth of the results from the SHETRAN Model were 0.606 m which occurred on January 17, 2013 in Tirta Rahayu Village, Sub-district Galur, Kulon Progo Regency. While the maximum height of flood inundation results from the RStudio analysis on the Progo Watershed range from 2001 to 2017 were 3,856 m which occurred in 2010.

Spatial analysis of the liquefaction vulnerability zone based on the phreatic level at the Palu groundwater basin, Central Sulawesi Province

An earthquake with a magnitude of 7.4 in Palu City and Donggala District in Central Sulawesi Province on September 28, 2018 has caused a liquefaction disaster. Basically liquefaction can occur in earthquake prone areas, shallow phreatic depth and poorly consolidated soil. This study attempts to examine the relationship between phreatic depth and the probability of liquefaction. The research method is an analog and numerical relation model, by combining the aquifer system model and groundwater geographic information system with landuse patterns in areas affected by liquefaction disasters. This method is described in Spatial and Environmental Analysis, which is supported by the use of satellite imagery and the analysis process with the Arc View Gis 3.3 program. The results showed that there was an influence between rainfall on the spatial distribution of phreatic depth, with the average rainfall in the Palu area being 68.74 mm / month and the depth of phreatic level ranged from medium (2.5 - 7.0 meters from ground level) - shallow (<2.5 meters from ground level). Based on the phreatic depth of the Palu groundwater basin, the chances for liquefaction are in the medium to high zone class.

Comparing phreatic evaporation at zero water table depth with water surface evaporation

Salt-affected soils are mostly found in irrigated areas within arid and semi-arid regions where the groundwater table is shallow. Soils of this type have become an increasingly severe problem because they threaten both the environment and the sustainable development of irrigated agriculture. A tool to estimate phreatic evaporation is therefore urgently required to minimize the salinization potential of salt-affected areas. In this context, phreatic evaporation at zero water table depth (E0) is a key parameter for establishing a model for calculating phreatic evaporation. The aim of this study was to explore the law of phreatic evaporation and to develop structurally rational empirical models for calculating phreatic evaporation, based on E0 data of six types of soil (i.e., gravel, fine sand, sandy loam, light loam, medium loam, and heavy loam) observed using the non-weighing lysimeter and water surface evaporation (E601) data observed using a E601 evaporator of same evaporation area with a lysimeter-tube at the groundwater balance station of the Weigan River Management Office in Xinjiang Uygur Autonomous Region, China, during the non-freezing period (April to October) between 1990 and 1994. The relationship between E0 and E601 was analyzed, the relationship between the ratio of E0 to E601 and the mechanical compositions of different soils was presented, and the factors influencing E0 were discussed. The results of this study reveal that E0 is not equal to E601. In fact, only values of the former for fine sand are close to those of the latter. Data also show that E0 values are related to soil texture as well as to potential atmospheric evaporation, the ratio of E0 to E601 and the silt-clay particle content (grain diameter less than 0.02 mm) is negatively exponentially correlated, and that soil thermal capacity plays a key role in phreatic evaporation at E0. The results of this analysis therefore imply that the treatment of zero phreatic depth is an essential requirement when constructing groundwater balance stations to study the law of phreatic evaporation.

Effects of planting Tamarix chinensis on shallow soil water and salt content under different groundwater depths in the Yellow River Delta

Groundwater is the main limiting factor that affects the growth and spatial distribution of vegetation in the Yellow River Delta, China. We carried out an experiment to investigate the effects of a Tamarix group and control group (bare soil, 0–20 cm) on shallow soil moisture, salt and salt ion distribution at various groundwater depths under brackish water salinity, and we simulated six different phreatic water depths (0.3–1.8 m). The results show that deeper groundwater depths decreased the soil water content, and the soil water content of the control group declined dramatically when the depth exceeded 1.2 m. However, when the phreatic depth exceeded 1.2 m, Tamarix presence mitigated the reduction in soil water content. A turning point in the water depth was also observed, and Tamarix exhibited water retention effects. The soil salt content presented converse S type as the phreatic water depth increased; Tamarix presence mitigated the reduction in soil salt content better than that in the control group. T. chinensis exhibited its maximum salt reduction range at a groundwater depth of 1.2 m. In the soil of the Tamarix group, the cations consisted mostly of Na+ and Ca2+, while the anions consisted mostly of Cl− and SO42−. The soil Cl−/SO42− ratio tended to decline along with the rise in the phreatic water depth. T. chinensis plantings resulted in easier leaching of shallow saline soils, which remained in a stable desalting state when the phreatic water depth was shallow (0.3–1.2 m); the shallow layers of the saline soil were converted to chloride saline soil. When the phreatic water depth was >1.2 m, the shallow soil was in a balanced state, and the main salt in the shallow soil consisted of sulfate salt; the soil salt content decreased, and the soil environmental quality improved. Therefore, when seedlings of T. chinensis are planted in coastal saline-alkali soil under brackish water salinity, the local phreatic water level should not be <1.2 m, as T. chinensis can effectively improve saline-alkali soils.

Empirical models of calculating phreatic evaporation from bare soil in Tarim river basin, Xinjiang

Based on the experimental data at the Akesu Water Balance Experimental Station (AWBES) from 1990 to 1996, the control conditions of establishing calculation models of phreatic evaporation have been analyzed, the empirical formulae for calculating the phreatic evaporation have been presented. The results show that as for a given phreatic depth, the phreatic evaporation increases nonlinearly with pan evaporation, when pan evaporation reaches the infinity, the phreatic evaporation is close to limiting phreatic evaporation. The new models overcome the disadvantages of phreatic evaporation overestimation when atmospheric evaporation demand is great and the linear relationship between phreatic evaporation and pan evaporation. With a high accuracy, the new models are appropriate to be applied in similar regions without observed data.

Groundwater chemical pollution risk: assessment through a soil attenuation index

Aquifer vulnerability is frequently estimated through methodologies that don't consider most physical and chemical soil parameters. A soil attenuation index is proposed to estimate groundwater chemical pollution risk, that takes into account organic carbon content, pH, cation exchange capacity, clay content, phreatic depth and land- scape position. The attenuation index is constructed by a methodology similar to that developed for water quality index. P, Mn and Zn concentrations in groundwater from selected places were used to validate the proposed index.

Specific yield for a two‐dimensional flow

We investigate the systematic secular spatial variation of specific yield. As a vehicle for this analysis we consider a canonical unconfined aquifer consisting of a porous zone whose cross section is a simple long rectangle. The hydraulic conductivity in the unsaturated zone is modeled by the quasi‐linear approximation. We find that locally the specific yield may be strongly influenced by the water table depth and mildly dependent on the recharge rate if that rate is high. For the simple geometry considered, a lateral component of flow has been found to have an insignificant effect on the local specific yield and that a model that assumes locally purely vertical flow to the given phreatic surface provides a more‐than‐adequate estimate of the specific yield. For the overall yield of an aquifer we find that the simplest model, wherein the flow through the soil is neglected, i.e., the model with static water and horizontal phreatic surface, provides a reasonable indication of the actual specific yield for most infiltration rates and aquifer dimensions. However, if the infiltration rate is high or the aquifer is particularly long, then the yield obtained from an assumed purely vertical flow, presupposing that the phreatic depth is accurately known, gives an excellent estimate of the actual specific yield.