ANALYSIS OF GROUNDWATER CHARACTERISTICS IN RIVERSIDE USING GROUNDWATER
- Slides: 19
ANALYSIS OF GROUNDWATER CHARACTERISTICS IN RIVERSIDE USING GROUNDWATER MONITORING NETWORK IN MIRYANG, SOUTH KOREA. MI KYUNG BAEK*, HYUN CHAE SHIN *, SANG MIN KIM** *GROUNDWATER & GEOLOGY DEPT. , KOREA RURAL COMMUNITY CORPORATION, S. KOREA **DEPT. AGRI. ENG. , GYEONGSANG NATL. UNIV. , S. KOREA
CONTENTS INTRODUCTION STUDY AREA METHODS RESULTS SUMMARY 2
INTRODUCTION 1. BACKGROUND ▪ Greenhouse uses the relatively high temperature groundwater(℃17~16) to reduce heating cost in winter season in South Korea. ▪ Greenhouse complexes are mostly located in riverside where groundwater are abundant. Greenhous e Groundwater supply Heat insulatio n vinyl Drip Greenhouse complex in study area. Groundwater heating system in greenhouse. 3
INTRODUCTION 1. BACKGROUND ▪ Most greenhouse complexes use groundwater as their main water supply in South Korea. ▪ In recent decades, greenhouse complex has increased, resulting in a groundwater shortages due to increase in groundwater usage. (ha) Greenhouse Areas by year (thousand, million tons) Groundwater usage by year Number Increase of greenhouse complex area in S. Korea Usage Increase of groundwater use 4
INTRODUCTION 2. OBJECTIVE ▪ For a sustainable groundwater use, systematic and quantitative management of groundwater resources is required. ▪ For this, groundwater monitoring network was established and the results was analyzed. ▪ The objective of this study was to analyze the variation of groundwater level, temp. , and EC using groundwater monitoring center sever monitoring well user Groundwater monitoring system (Left : remote control and monitoring system, center : Schematic diagram of monitoring well, right : monitoring well. Each data is received per hour automatically with solar system. ) 5
STUDY AREA 1. LOCATION ▪ Study area, Miryang, is located in southeast of South Korea. ▪ The location is 60 km upstream from the mouth of the Nakdong River. 2. SOIL FORMATION ▪ Alluvial strata ranges to 30 meters below ground surface, and bedrock is formed below the alluvial strata. 6
STUDY AREA 4. GROUNDWATER CHARACTERISTICS ▪ Salt is accumulated in deep sedimentary rock near the riverside due to longterm tides from the East Sea. ▪ The deeper the depth, the higher the salinity. ▪ Cation-anion distribution analyzed to determine the origin of groundwater. • The distribution of shallow groundwater is similar to that of surface water. • The distribution of deep groundwater is shown in the seawater penetration zone. shallow well deep well Piper-diagram of groundwater cation-anion analysis. 2 wells is located in same site, 3 m apart. 7
METHODS 1. ANALYSIS BY REGION DIVISION ▪ The 31 monitoring wells were categorized by 3 regions: riverside, mountain, and plane. Location of 31 monitoring wells. Riverside(11) Mountain(6) Multi-depth(4) (included in riverside) Plane(14) 8
METHODS 2. ANALYSIS BY DEPTH • 4 monitoring wells were selected for detailed analysis of EC variation due to salt penetration near the riverside. • 3 sensors were installed at different depths in each wells. - Installation depth : EC transition depth, the upper and lower depth by EC logging in each wells. - Period: Jul. /2017~Nov. /2018 Multi-depth monitoring started 2 sensors are added in monitoring well. Total 3 sensors are in different depth. 9
RESULTS 1. THREE REGIONAL ANALYSIS 1 -1. GROUNDWATER LEVEL ▪ Riverside Region • Constant variation pattern, decrease in winter. • Drawdown during greenhouse heating period. - SW (10 m) < DW (20 m) - Drawdown at the same time but DW recovery later than SW. DW’s G. level recharge delay due to low hydraulic conductivity. ▪ Mountain Region • 1~3 m below the surface. • Not constant. • Relatively high level due to hig altitude. ▪ Plane Region • 2~11 m. • Drawdown & recovery repeated daily, but no significant changes. • Normal waterlevel at atmospheric pressure. Observation result of Water level 10
RESULTS 1 -2. EC ▪Riverside Region • Different by depth. • 2 wells in same site, the deeper the depth, the higher the salinity. • Almost constant. ▪ Mountain Region • Common range of deep well. - EC : 170~200㎲/㎝, freshwater quality • Almost constant. • Low permeability less affected by the surrounding environments. ▪ Plane Region • 300~500㎲/㎝. Constant. • Common range of deep well. Observation result of EC. 11
RESULTS 1 -3. TEMPERATURE ▪Riverside Region • Different results depending on depth. - SW : Constant pattern, high in winter, low in summer in natural groundwater condition. - DW : Constant pattern regardless of season. ▪ Mountain Region • Common range of deep well. - Temp. : 15~16 ℃ • Almost constant. • Low permeability less affected by the surrounding environments. ▪ Plane Region • 16~17℃. Constant. • Common range of natural groundwater. Observation result of Temp. 12
RESULTS 2. EC ANALYSIS BY DEPTH 2 -1. NEAR THE NAKDONG RIVER(MYM-09) • From 4, 000 to 11, 000㎲/㎝. • EC increased sharply in the period of groundwater supply for heating the greenhouse. • EC in the deepest(75 m) increases first and recovery last, contrary top(20 m) is not changed due to dilution of surface water. And the EC of the aquifer(40 m) has risen to its maximum and repeated daily changes. • It means salt penetration is the longer at deeper depths. greenhouse heating period Result of EC of MYM-09 in (R). 13
RESULTS 2 -2. SECONDARY TRIBUTARY OF NAKDONG RIVER(MYM-06) • EC increases sharply when the greenhouse heating began. (700~5, 500㎲/㎝) and the value of EC is higher at deeper depths. • The EC value rises at the same time(this means all depth have same hydraulic conductivity) but the top of the three depths(30 m) is restored first and the bottom(60 m) is finally restored. • Repeated long-term salt penetration and recovery will eventually increase groundwater salinity accumulation. greenhouse heating period Result of EC variation in MYM-06 in (R). 14
SUMMARY 1. Different monitoring results depending on the region. 1) Riverside(R) ▪ Wells in (R) are influenced by precipitation and river flow usually. ▪ Water level, Temperature : constant pattern due to high permeability coefficient. ▪ EC : different by well depth. • Shallow well : not constant due to river quality changes. • Deep well : constant pattern, fall in winter and rise in summer. 2) Mountain(M) ▪ All is observed no big change relatively. ▪ Low permeability. Less affected by the surrounding environments. ▪ Common in deep well. 3) Plane(p) ▪ Temperature : common range of natural groundwater. ▪ Water level : repeat drawdown & recovery daily, but no significant changes. ▪ EC : common waterlevel at atmospheric pressure. 15
SUMMARY 2. Multi-depth monitoring analysis in (R) 1) Near the Nakdong River(MYM-09) ▪ MYM-09 is observed high salinity usually due to near Nakdong river ▪ Groundwater levels down and EC rises sharply due to the use of groundwater concentrated in winter season in many greenhouses. ▪ But, due to the inflow of surface water from the Nakdong River, the drawdown width is small, and the water quality change of the upper layer is not large. ▪ Salinity large increases and daily changes in the major aquifer(60 m) indicate active salt penetration through the high hydraulic conductivity. ▪ Repeated long-term salt ‘penetration and recovery’ may eventually increase groundwater salinity accumulation. 16
SUMMARY 2. Multi-depth monitoring analysis in (R) 2) SECONDARY TRIBUTARY OF NAKDONG RIVER(MYM-06). ▪ Similar pattern to MYM-09 because it is located in the riverside greenhouse complex too. ▪ Because relatively far from the Nakdong River, EC is relatively low and the groundwater level change is large. ▪ Unlike MYM-09, the simultaneous EC increase of three depths means that the hydraulic conductivity is uniform. ▪ The large change in groundwater level and slow recovery is due to the relatively low hydraulic conductivity and insufficient river flow amount. ▪ Multi-depth monitoring is required in areas where salt penetration is a concern. 17
SUMMARY ◆ For stable use of groundwater ▪ Sufficient surface water inflow during periods of high groundwater use may maintains the groundwater level and delay the penetration of dense salt water from the bottom. ▪ But, if the groundwater is used more than the surface water inflow, salt penetration will inevitably arise. ▪ In the long run, there will be a shortage of groundwater, the top of the groundwater will turn into brine and will not be available for agricultural water use. ▪ Stable groundwater use requires not only changes in groundwater levels but also long-term observations of changes in water quality due to brine penetration and long retention time. 18
Thank you. *Groundwater & Geology Dept. , Korea Rural Community Corporation, S. Korea dodocuma@gmail. com **Dept. Agri. Eng. , Gyeongsang Nat. L. Univ. , S. Korea 19
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