GROUNDWATER DEVELOPMENT IN THE MOUNTAIN SKIRTS
OF VOLCANIC MASSIFS IN EASTERN JAVA, INDONESIA
KAZUKI TSUJI
Fuji Grouting Engineering Co., Ltd.
Fukuoka, 810-0041, Japan
INTRODUCTION
The area of the East Java Groundwater Development Project is located in the eastern part
of the Java Island covering the majority of the province of East Java (Figure１). The
Madiun－Solo and Madura are excluded, even though they are in the same province.
This project was executed from 1982 to 1986, and run up to present independently by the
Indonesian Government, extending objectives in step-wise into promising and poorly
developed areas of groundwater. This thesis presents the project as an example of a
large-scale groundwater development in the mountain skirts of volcanic massifs erupted
in the younger geologic age, with special attention to aquifer systems and project
management.
Figure 1. Location map and development area according to the stage
BACKGROUND OF THE PROJECT
In the province of East Java, three investigation schemes of groundwater development for
supplement irrigation water were started in the area of Kediri-Nganjuk, Maduin- Solo,
and Madura in 1972. In conclusion a series of pilot project construction and studies was
commenced under the evaluation of feasibleness. The implementation was continued in
step-wise till 1981.1n 1976 a groundwater survey of the whole province of East Java was
started, which were concentrated to the areas where water shortages existed and
groundwater potential was expectable. The study result indicated in 1979 that there were
potential areas of 15,000-20,000 ha in total within the studied areas which could benefit
from groundwater development. In 1982 IBRD agreed to finance the project for the
implementation of the groundwater development in the area in the East Java, except
Maduin-Solo and Madura. The area stretches 350km in the east-west direction then
160km in the north-south, encompassing an area of 47,900km²of land, where 31 million
people are populated、mainly engaging in agriculture. The climate is typical of East Java
with marked wet (Nov. to Apr.) and dry (May to Oct.) seasons. Precipitation totals
2200mm in south coast, contrarily 1150mm in north, 70 % of which is concentrated in
wet season. The dry season water is the main constraint on the agricultural productivity.
The project aimed at increasing the productivity of paddy and other profitable crops not
only in dry season but also in transition term by way of stabilizing water supply using
exploited groundwater. The project was supervised by the Consultants under
administrated with P2AT (Groundwater Development Project) office, Ministry of Public
Works, Indonesia.
PROJECT IMPLEMENTATION
The ordinary way of executing a water resources development project is that the
implementation follows a sequence of stages of works as follows, A) Investigation and
survey stage, B) Planning stage C) Pilot development stage, D) Development stage, E)
Agriculture exploitation stage. However for this project the way of performing was
adopted differently. There was not an orderly sequence of stage and contrarily several
stages were employed in the same time. Furthermore the project area involved broad and
widespread regions, which exhibited a variegated and complicated geohydrological
background and investigation history undergone in the past, and hence the project area
was for convenience divided into the following categories (Figure 1) i.e.,
1）Implementation stage: Kederi-Nganjuk Zone
2）Extensive pilot development stage: Mojokerto- Zone, Tuban Zone
3）Pilot development stage: Pasuruan Zone, Probolinggo Zone
4）Investigation and study stage: Jember-Lumajang Zone, Situbondo Zone and others
Accordingly it was naturally realized that for the sake of elucidation of groundwater
resources in the project area, a different methodology was envisaged and adopted
depending upon the data available on hand. Brief work schedule of the project was as
follows (order was not necessarily actual),
1) procurement of equipment and materials, 2) workshop rehabilitation and preparation,
3) drilling operation, 4) pump installation and on-farm works, 5) operation of well, 6)
agriculture, economics, water management, 7) hydrology, 8) geohydrology, 9) irrigation
study and design, and 10) final report.
CONSULTANT’S ACTIVITY
The engineering service for the project was started in 1982 under the international
associated consultants firms, Nippon Koei Co., Ltd., in Tokyo, Electroconsult S.p.A., in
Milano and P.T. Wiratman in Bandung. The activity of the consultants covered
approximately 14 specialities for the foreign consultants, portioning 219 men/month,
equivalent to 39 % out of total 566 men/month. Then about 9 specialities in the
Indonesian consultant, sharing 347 men/month.
GEOGRAPHY
The project area is characterized by conspicuous physiographical zone trending roughly
east to west, which is attributable to the zonal geological structures in the Island. These
parallel zones are designated as follows from north to south (Figure 2).[1].
1）The Rembang zone
2）The Radublatung zone
3）The Kendeng zone
4）The Solo zone
5）The Southern Mountain zone
On the northern part of the province occur the Rembang hills and the Kendeng hills
to thewest of the city of Surabaya. The lower reach of the river Bengawan Solo meanders
fromwest to east between these two hill masses forming a widespread alluvial plain. The
central part of the province is dominated by a volcanic mountain chain ranging in height
from 2800 to 3600 m running through from east to west direction at a distance of about
every 60 km. The highest volcano, Mt. Semeru soars 3675m above sea level. The
Southern hill masses extend along the southern coast. The river Kali Brantas originates
from the volcano Mt. Arjuna and discharges westward between the southern foot of
volcanoes and the Southern hills at its upper reach and turns toward northwest. A vast
alluvial plain stretches along the middle reach of the Kali Brantas, extending the widest
intermontane groundwater basin between the volcanic massifs of Mt. Wilis and Mt.
Arjuna-Mt.Kelud, such that the other volcanoes are surrounded by the extensive gently
undulating slopes.Then the Kali Brantas turns clockwise again toward the east flowing
between the Kendeng hills and the northern border of the volcanic slopes. Alluvial deltas
are developed at the estuary of these large rivers, where seacoast is fringed with marsh
land, where the capital city of Surabaya is located. Some of the volcanoes are still active,
like Mt. Kelud, and some others are dormant.
Figure 2. General geology of East Java
GEOHYDROLOGICAL BACKGROUND AND AQUIFER SYSTEM
The general stratigraphy in the main project areas is shown in Table 1.[2],[3].
The Miocene formations in the upper-Tertiary period, which are widely present in
the area, are expected to be the oldest in the area. They are characterized by enormous
volume of carbonate rocks, limestone and marl. Some of the formations produce notable
groundwater to exploit like Tuban and Kawengan formations in Rembang area. In the
Rembang hills along the north coast, there occurs limestone with high porosity of cavities,
which are productive in groundwater. The Southern hills are mainly composed of
limestone of Miocene epoch, showing poor potential of groundwater due to stiff
compacted litho-facies.
Major aquifers are contained in the formations deposited in the Quaternary period.
The intermontane basins, which widespread surrounding the volcanic massifs,are
extensively underlain by volcanic rocks, pyroclastic rocks and their secondary sediments,
which are originated from successive volcanic activity(Figure 3). Parallel to the
alignment of the Kendeng hills sedimentary rocks of the Kabuh Formation belonging to
the Pleistocene epoch crop out with a strike of east-westward, dipping gently southward,
then submerging under the intermontane basins. The geological relation between the
above-mentioned successions of the rocks are extremely complicated area by area, but as
a whole they are mutually interfingered under the alluvial plain and the intermontane
basins down below the Kali Brantas river, containing several horizons of deep aquifers
with high potential. They are weakly cemented pyroclastic flows associated with their
derived deposits and coarse sediments such as conglomerate and sandstone of the Kabuh
Formation. These aquifers are extensively and unconfomably underlain by impervious
clayey stones corresponding to the Pucangan Formation.
Table 1. Brief stratigraphy of the main project areas
Moreover shallow aquifers are developed extensively in the area, originated from
fluviatile washout from the surrounding volcanoes and river deposits. Basically aquifer
system in the area is composed of two-stories structure of shallow and deep aquifers
intersected by interbedded impervious layers. The subsurface lithology below the alluvial
plain along the Bengawan Solo is dominated by silty to clayey deposits, containing
scarce groundwater.
A drilled well penetrating 100 to 150m deep down to the above-mentioned aquifers
is able to abstract 30 to 60 l/sec of groundwater, furnishing 45 ha of irrigation per well in
average. Transmissivity in the main groundwater basins stretching Kederi down to
Mojokerto ranges in m²/day from 300 to more than 2000, equivalent to from 2 to more
than 10 ℓ/sec/ｍ in specific yield at maximum in the same area.
Figure 3. Diagrammatic geological section near Mojokerto (north to south) and legend
Figure 4. Geohydrological map of Tuban Zone(East), Northwest of Surabaya
Seawater intrusion: The investigation to date indicate that groundwater is
developable with high potential in the seacoast aquifer belts, specially in Tuban,
Pasuruan,
Probolinggo and other eastern spur of the East Java. However sea water intrusion
constrains to proceed with groundwater development if it is unfavorably tackled with.
Accordingly the sea water intrusion study has been undertaken as an upgrading program
to firstly reveal the present conditions of sea water encroachment below the seacoast
aquifer belts in Tuban, Pasuruan and Probolinggo zones (Figure 4,5). Eventually the
outcomes obtained by the study enabled to contemplate a prevention tactics against sea
water intrusion, coupled with taking a concept of safe yield of development into
consideration. The study is concentrated in Tuban zone, where the development
area ,rising up less than 20 m in elevation above sea level, lies about 7 to 10 km away
from the Java sea to northern hilly hinterland. Some wells likely to induce saline water
when pumping water levels lower below sea mean sea level at the rate of 50ℓ/s yield.
Such jump-up of the values near the bottom in the limestone or clayey formations
lead to speculate that the brackish waters are likely to be connate water entrapped in a
clay, presumably not direct from sea water intrusion. The electric conductivity loggings at
the time show that there occurs no sea water intrusion at the time, however there exists
the water indicating high electric conductivity ranging in micro-mho/cm from a few
thousands to about 10,000.
Figure 5. Geohydrological map of Pasuruan Zone, East of Surabaya
Pasuruan-Probolinggo zone: The Pasuruan-Probolinggo zone lies to southeast of
Surabaya, occupying an area of 92,000 ha and stretching 3 to 10 km wide strip of the flat
plain along the Madura seacoast (Figure 5). The development areas are mainly present in
the south of the plain, where the relief rises gently to the lower slopes of the volcanic
massifs soarining higher than 3000m.The geology of the zone is basically characterized
by enormous volume of the Quaternary volcanic products of variegated facies and
composition, which are extensively underlain by the Pucangan and Kabuh formations.
The aquifers are contained in the lava complex and pyroclastic flows. Sea water intrusion
during development stage is interpreted.
LAND USE AND SOCIO-ECONOMIC CONDITION
The alluvial plains, the lower slope of the volcanoes and the intermontane basins are well
cultivated. Agriculture is the major economic activity and 70 percent of the population is
directly dependent on it. Some 925,000 ha of land are presently irrigated mostly diverting
river flows. 33% of the cultivated lands are categorized as paddy field (724,000 ha).
Three crops per year are possible in lands advantaged with river water irrigation.
However the rest of the land remains on either double-cropped per year at maximum or
merely rain-fed. An independent farmer reaches 78% of all regarding land tenure and an
average farmer holds a size of 0.3 ha land. A crop is of rice in wet season and maize,
peanut, soybean and red pepper etc in other seasons. Water users cooperative is organized
per well to maintain a pump and canal facilities.
PROJECT PERFORMANCE
The project integrated final results in 1986, concluding that 6,250 ha land proposed by
the Consultants was irrigable by groundwater on a basis of simulation model analysis and
moreover economic evaluation resulted in further extension of 10,500 ha was feasible
area by area. Water balance between groundwater and surface water was evaluated to
maintain sustainable development of groundwater.
STRATEGY AND TECHNOLOGY
Indonesian government organized Groundwater Development Project(P2AT),under the
Directorate General of Water Resource Development, Ministry of Public Works in
early-70s and it has functioned as the executing agency of the implementation of the
groundwater development project. Later the Agency was handed over to provincial level,
where 17 offices have activated and engaged in many kinds of groundwater projects.
Many of the staffs have job-hopped and worked as a consulting engineer in the private
sector. Technology and management capability acquired by the Indonesian experts
through the projects have been passed on to younger generations, implementing a great
deal of groundwater development projects, which have expanded objectives not only
from a large scale of irrigation to a small scale of domestic water supply, but also areas
from East Java to relatively less-developed remote islands. Some of them noted here are
rural water supply in Lombok Island, Nusa Tenggra, Sulawesi Islands.
REFERENCES
[1] Van Bemmelen.,R.W.“The geology of Indonesia” ,Government Printing Office, The
Hague, pp8-12,(1949)
[2] Tsuji,K“East Jawa groundwater development project”, vol.3,Annex-4,Geohydrology,
p203, in Nippon Koei Co.,Ltd., Electrocosult S.p.A., P.T.Wiratman and Associates
Report(1986)
[3] Kumazawa,K. “ Quaternary geology and hydrogeology of the Madiun basin,
Indonesia” , Journal of Geoscience, Osaka City University, Vol.37,Art.8, pp213-242,
(1994)