IncorporatedIncorporated AdministrativeAdministrative AgencyAgency JapanJapan WaterWater AgencyAgency ToneTone RiverRiver DownstreamDownstream ArealAreal ManagementManagement OfficeOffice Dynamic Lake Kasumigaura Lake Kitaura Lake Nishiura Outline of Lake Kasumigaura Wani River Kitatone River Lake Sotonasakaura ○History of Lake Kasumigaura ○Outline of Lake Kasumigaura Hitachi River Lake Kasumigaura is located about 60km away from Lake Tokyo and in the southeastern part of Ibaraki Prefecture. It 2 2 Lake Nishiura 168.2km , Lake Kitaura Approx. 220km 2 2 is the second largest freshwater lake in Japan. Total space 35.0km , Hitachitone River & others 15.3km Lake Kasumigaura was a part of the Pacific Ocean with Total coastal line 250km Lake Nishiura 121.4km, Lake Kitaura 63.9km, downstream area of Tone River, Lake Inbanuma and Lake length Hitachitone River 64.6km Teganuma about 6,000 years ago. Later, sediment supplied Total capacity Approx. 850 mil. m3 at the time of Y.P.＋1.0m from Tone River has separated these lakes from the ocean Max. depth 7m Average depth 4m and made Lake Kasumigaura what it is today. Water exchange Approx. 200 days ○Hydrological/meteorological characteristics Basin The Lake Kasumigaura basin area belongs to East Japan Type climatic zone. In winter, north-west seasonal winds Basin area 2,157km2 Approx. 1/3 of Total Ibaraki Pref. (6,097km2) called “Tsukuba Oroshi” tend to blow down from Mt. Total # of municipality 24 Ibaraki Pref.(17 cities, 4 towns, 1 village), Tsukuba and sunny days tend to last, and there is limited Chiba Pref. (1 city), Tochigi Pref. (1 town) amount of rainfall. In summer, south-east seasonal winds # of municipalities Ibaraki Pref.( 10 cities, 1town, 1village), surrounding the Lake 13 Chiba Pref. (1 city) blow up from the ocean and they bring relatively large Annual mean rainfall 1,244mm Annual average rainfall in the basin (1996-2015) amount of rainfall. There are few regional differences in *In this chart, three lakes respectively named "Lake Nishiura", "Lake Kitaura" and "Lake the temperature in this basin area except for the mountain Sotonasakaura" and three rivers named "Hitachi River", "Kitatone River" and "Wani River" all combined make up "Lake Kasumigaura". areas and annual mean temperature is around 13 degrees Celsius. Average annual rainfall is 1,257mm, comparatively ○Flood in Jun-Jul 1938 Y.P. +3.34m (Downflow flooding) smaller than national average of 1,700mm. - The total amount of rainfall in the Lake Kasumigaura basin area caused by the typhoon reached 400-500mm. - The total amount of rainfall in the mountain area of the Tone River ○Characteristics of the lake system was 100-200mm. The surrounding area of Lake Kasumigaura is low-lying and - Downflow flooding occurred As the cross section of Hitachitone River was small, inundation in the ill drained. Therefore, this area has struggled with repeated area around Lake Kasumigaura continued for dozens of days. floods. In addition, since this area is located close to the -Damages 2 sea and subject to the sea tide, this area has also struggled The inundated area totaled approx. 2,145km in the entire Tone River system. Damages to the agricultural production in the Lake Kasumigaura basin with the severe salt damages and droughts. Especially, the area reached 13.6 million yen (equivalent to the present value of 20 floods in 1938 and 1941, and the salt damages extended billion yen.) to approx.1,140 ha in 1958 which arose from the severe ○Flood in Jul 1941 Y.P.+2.90m (Backflow flooding) drought caused significant damages in this area. - Rainfall caused by the seasonal rain front and typhoon (more than In terms of the water quality, as the lake has an extended 300mm of rainfall in the Kinu River and Watarase River basins, which are located in the mid-stream area of Tone River basin) basin area and its depth is rather shallow, it is subject to - Rainfall in the Lake Kasumigaura basin was relatively small as opposed water pollution or eutrophication. to the mid-stream area of Tone River. - Backflow flooding occurred. The backflow from Tone River flowed into Lake Kasumigaura and caused ○Socio-economic aspect of the basin the flood damages shown below. The Lake Kasumigaura basin area extends over 24 -Damages municipalities in Ibaraki, Chiba and Tochigi prefectures and Inundated houses in Tsuchiura exceeded 1000. Inundated houses in Hokota exceeded 200. its basin area coverage is equivalent to just about one third The 2,000 ha of farmland was totally submerged around Kitaura, and a of total area of Ibaraki Prefecture, i.e. 2,157km2, and its wide range of farmland around Nishiura was also submerged. population reached approx. 960,000. ■ Salt damages on the agriculture The basin area was mainly developed for farmland and Item Damaged Damage space amount Remarks rice growing, lotus root growing and hog raising, etc. are its Year (ha) (K yen) major lines of businesses. 1957 315 4,161 Salt damage (in May) in Kamisu Village 1958 1,139 32,265 Salt damage(Jun-Aug) Kashima, Namekata, Inashiki-Gun Agriculture in this basin has been promoted since Edo 1960 365 8,847 Salt damage(Jul) Kashima, Namekata, Inashiki-Gun 1961 118 1,866 Salt damage(Jun) Kashima, Namekata, Inashiki-Gun Period. But as the agricultural lands developed in this basin 1962 74 2,467 Salt damage, Kashima, Namekata, Inashiki-Gun 1963 372 9,133 Salt damage, Kashima, Namekata, Inashiki-Gun are basically located in the low-lying area, farmers have 1964 124 1,648 Salt damage, Kashima, Namekata, Nanbu Region struggled with the floods for long years. 1966 50 1,636 Salt damage, Kashima, Namekata, Nanbu Region 1967 595 10,120 Salt damage, Kashima, Namekata, Nanbu, Seibu Region After the World War II, to meet the socio-economic 1973 14 － Salt damage in Aug in Okinosu Hitachi River basin 1974 496 － Salt damage (in May-Sep) in Kitaura, Hitachi River basin development in Japan, new rice fields were developed *The amount is calculated based on the value of 1975 year. along the lake by reclamation to increase food production. ■ Demographics of Kasumigaura Basin Nowadays, the downstream area of the lake is one of the （Unit:10,000 people) 0 10 20 30 40 50 60 70 80 90 100 richest grain-yielding areas in Kanto Plain. 1960 62.3 Population of the basin When it comes to the industrial aspect, along with the 1965 60.6 muniicipalities 1970 63.3 high economic growth started from the latter half of 1975 70.6 1980 78.3 1950s, development of Kashima Coastal Industrial Zone, 1985 84.8 construction of Tsukuba Academic City and construction of 1990 90.2 1995 95.6 Joban Expressway and Higashikanto Expressway stimulated 2000 96.0 the urbanization in this area. As a result, the total value of 2005 97.2 2010 97.5 industrial shipment increased and reached 5.6 trillion yen 2012 97.9 2013 97.3 according to the Ibaraki Prefectural Statistics Yearbook 2014 96.7 2013. 2015 96.4 Lake Kasumigaura Development Project ○Project Outline ○Objective of the Project Since Lake Kasumigaura was originally an inlet of the The Lake Kasumigaura Development Project is the one Pacific Ocean surrounded by low-lying area, this area has to control floods and newly develop water resources using struggled with repeated floods and salt damage. On the effective reservoir capacity of 617 million m3, from the other hand, along with the rapid economic growth, the local water utilization lower limit water level of Y.P. ±0.0m to the industries developed and the population and water demand planned high water level of Y.P. +2.85m. in this area increased. The Lake Kasumigaura Development Project was planned ○Flood Control to protect the livelihoods of people from floods and salt During the summer restriction period (from June 1 to July damage, and meet the increasing water demand. In 1971, 31 every year), the water level is restricted to Y.P. +1.20m Water Resources Development Public Corporation took over or less and 361 million m3 of flood control capacity are the project from Ministry of Construction, and the project secured. In addition, during other periods as well, the water was completed in March 1996, 25 years after the start of level is restricted from Y.P. +1.30m to Y.P. +2.85m and 339 its construction. million m3 of flood control capacity are secured. ○Construction Details ○Water Utilization The Lake Kasumigaura Development Project consists of Designatedirrigationwater: Using 156 million m3 out of construction work of the lake shore levee, renovation work the reservoir capacity of 278 million m3 (256 million m3 of the Hitachi River Sluice Gate, river improvement works in the summer period), with a lake water level from Y.P. ± and construction and renovation works for compensation. 0.00m to Y.P. +1.30m (Y.P. +1.20m in the summer period), ①Lake shoreleveeconstructionwork: Lake shore levee an average of 19.56 m3/s are supplied to agricultural land whose length was 78km and elevation was Y.P.+3.00m in Ibaraki Prefecture and Chiba Prefecture for irrigation was newly constructed on the section of lakeshore during the irrigation period. where there had been no levee, and the existing levee Municipalwater: Using 172.4 million m3 out of the reservoir revetment was reinforced. capacity of 278 million m3 (256 million m3 in the summer ②HitachiRiverSluiceGaterenovationwork: Due to the period), with a lake water level from Y.P. ±0.00m to Y.P. necessity of securing reservoir capacity, and to prevent +1.30m (Y.P. +1.20m in the summer period), at most salt damage going upstream through gate operations 3 7.791 m /s is supplied to Chiba Prefecture and the associated with the project, the lock part was modified Tokyo metropolitan area for domestic use, and at most through construction of a small lock gate and a 15.569 m3/s are supplied to Ibaraki Prefecture and Chiba desalination facility, and a spare gate was manufactured.