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Open Access Discussions Sciences , M. Sumaryono Earth System Earth 2 Hydrology and and Hydrology , H. Hidayat 6 1,7 ) in Southeast Asia humid tropic with 2 2826 2825 1000 km < , C. K. Shum 1 , and S. Sunarso 5 , K.-H. Tseng , F. Setiawan 1,3,* 3,4 This experiment proves that satellite altimetry provides a good alternative, or the To address this scientific challenge, this study tries to monitor small (40–200 m width) This discussion paper is/has beenSciences under (HESS). review Please for refer the to journal the Hydrology corresponding and final Earth paper System in HESS if available. Division of Geodetic Science, School of Earth Sciences, TheHydrology Ohio and State Quantitative University, Water Management Group, Wageningen University, Wageningen, Department of Forest Science, UniversityDepartment of of Mulawarman, Samarinda, Global Agricultural Indonesia Sciences,Research The Center University for of Limnology, Indonesian Tokyo, Japan InstitutePT of Vale Indonesia, Sciences, Cibinong, Tbk, Indonesia Sorowako,Institute Indonesia of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, China now at: Hydrological Sciences Laboratory, NASA Goddard Space Flight Center, A. Suhardiman 800 m width) andreasonable small accuracy. lake In (extent addition, thewater procedure level heights to via choose identification or retracked selectionwater Envisat of is altimetry standard recommended waveform shapes and for should inland and be a lakes. standard This measure especially studyreported over by also small previous rivers studies, found among thatfor the Envisat four Ice-1 radar standard altimetry is waveform retracking observing not algorithms inland necessarily water bodies. the best retracker as of Southeast Asia,and specifically makes use in Level Indonesia, 2Agency’s radar (ESA’s) where Envisat altimeter (Environmental similar measurements Satellite) generated studies mission. by do European Space notonly yet means exist in some regions, to measure the water level of medium-sized river (200– satellite radar altimeterthan footprints 1 limit km. Some the studiessize water indeed rivers level reported measurement as successful narrow for retrievalsignals of for rivers as small water wider 80 water level m; bodies for however, to small- the retrieve accurate processing water levels, ofand remains medium-sized current challenging. (200–800 m satellite width) altimetry identification rivers and and lakes choice using of satellitepropriately altimetry the through waveform-retracked over-water water radar waveforms level. corresponding This to study the addresses ap- the humid tropics Remote sensing and satellitetoring geodetic of observations freshwater resources. are For capable theresolutions for case (e.g., of hydrologic satellite satellite moni- radar revisit altimetry,weekly) period) limited interval temporal prohibit monitoring the of use water of level or this discharge. method On for the a other short hand, ( the current Abstract Satellite radar altimetry for monitoring small river and lakes inY. Indonesia B. Sulistioadi Hydrol. Earth Syst. Sci. Discuss.,www.hydrol-earth-syst-sci-discuss.net/11/2825/2014/ 11, 2825–2874, 2014 doi:10.5194/hessd-11-2825-2014 © Author(s) 2014. CC Attribution 3.0 License. 1 Columbus, OH, USA 2 the Netherlands 3 4 5 6 7 * Greenbelt, MD USA Received: 17 January 2014 – Accepted: 21Correspondence February to: 2014 Y. B. – Sulistioadi Published: ([email protected]) 10 MarchPublished 2014 by Copernicus Publications on behalf of the European Geosciences Union. 5 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | - β orts ff orts. ff average discharge and 200– 1 − s 3 2828 2827 set correction (Tseng et al., 2012). ff 1 km width (Birkett, 1998; Birkett et al., 2002). Even average discharge, respectively, according to Mey- ∼ 1 − s 3 orts to monitor watershed hydrology. Copious research has ff set Center of Gravity (OCOG) or Ice-1 (Wingham et al., 1986) is a simple but ff set Center of Gravity (OCOG) (Wingham et al., 1986), also known as Ice-1, ff After all, there is no “one size fits all” method for satellite altimetry waveform re- The early use of satellite altimetry to retrieve water level of the river utilized waveform The O Satellite altimetry missions were introduced to support studies of oceanographic Space geodetic and remote sensing from space has proven to be one viable source 100 m width (e.g. Kuo and Kao, 2011; Michailovsky et al., 2012), satellite altimetry lakes. This led to the integration of geospatial information, remote sensing and satellite for Envisat radar altimeter sensorclaimed ntil the Envisat best was available decommissioned2006). retracker in Some for June notable medium 2012 recent to and developmentsthreshold of large-sized retracker inland rivers water (Davis, (Frappart retracking 1997)2009), et methods sub-waveform and include al., analysis (e.g. its Hwang et improvementsand al., sub-waveform (e.g. 2006 filtering and Lee, and Fenoglio-Marc track 2008; et o al., Bao 2009) et al., tracking available up towater level now, of small especially (40–200 m those width) devoted and to medium-sized (200–800 measuring m width) near-real rivers and time and Remy, 1997). robust retracker, which requires onlynot the require any statistics model; of hence it thealgorithm, is waveform later which samples called model-free later and retracker called does (Bamber, 1994). as This Ice-1, was still carried out as one standard retracker government from relying to this method to monitor rivers. shape to match thereturned specular by characteristics, the which river (Koblinsky exclusively etof belongs al., retrackers to 1993). for Along non-ocean the with studies signals the this were principle, completed O the in development the lastvolume decade, scattering which retracker includes (Davis, 1993),retracker (Zwally, Sea 1996), Ice surface/threshold retracker retracker (Laxon, (Davis, 1994), 1997) NASA and Ice-2 (Legresy some studies present successful∼ retrieval of water levelsignals of processing small-sized rivers for down smallwith to significant water improvement bodies on stillporal the remains resolutions measurement challenging. of accuracy, Therefore, the limited even spatial current and satellite tem- altimeter missions still prevent scientist and measurement into only rivers with ment of hydrology studies; for example, the current radar altimeters footprints limit the phenomenon (Brown and Cheney, 1983) even thougha at way the to later stage study scientists largehad found inland been water made bodies (Fusions since and (Wingham a Cazenave, and 2001). couple Rapley, Numerouswell 1987; decades e as Koblinsky ago the et to recent al.,frenne, satellite utilize 1993; 2003; altimetry Morris early Kouraev missions and et satellite (e.g.Cretaux Gill, al., altimetry et Birkett, 1994), 2004; al., 1998; mis- 2011) as Calmant to Benveniste and monitorvarious and the Seyler, De- hydrology limitations 2006; of large of Frappart river et and space lake al., systems. geodetic 2006; However, observation systems hampered the advance- parts of thedemonstrated world, the in capability e of remotely-sensedof data a to provide number continuous ofdevelop estimation global hydrological rivers’ variables and (Tangnot lakes’ et none water of al., level them database 2009). count exist small A to to number date, medium-sized rivers but of and very initiatives lakes limited in to if the humid tropics. beck et al., 1996) aroundLettenmaier, the 2003). world are In poorly contrast, gaugedsurement, for despite such various permanent the reasons gauging installation (Alsdorf is and andthe often considered operation need costly of and for less in-situ continuous importantfore, mea- it hydrological while is monitoring a of scientificinformation small and given social the rivers challenge absence is to of increasing. continuously provide operating reliable There- in-situ water measurement level and e of observation discharge to complement or replace field measured data, which is lacking for many Water level (also calledthe stage) quantity and of discharge fresh are waterrivers resources. essential A (defined parameters tremendous as in number800 of monitoring 40–200 m m small width to width and medium-sized with 100–1000 m 10–100 m 1 Introduction 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | S N 0 0 00 34 erent ◦ ◦ ff 920 km and 23’ to 2 ∼ ◦ E longitude and 1 0 30 ◦ E longitude and 2 0 to 117 29 0 ◦ 40 ◦ to 121 0 2830 2829 ). With its maximum depth of 595 m and mean 2 12 ◦ , which declares this river as the second longest river both 2 N latitude. Mahakam is its main river that stretches a length of 0 45 ◦ ected by ocean tide that intrudes through the Mahakam Delta. These factors led to Karangmumus River is a very narrow channel (3 to 45 m width), which is very im- ff fault that forms veryLake limited Matano number has of two alluvial flat plain. depressions Regarding separated the by bed a topography, saddle. Lake Matano drains despite its small extent (i.e. onlywater 164 km surface elevationtodepression measured which at essentially only means(Hehanussa and 392 its Haryani, m, 1999). bed Originated Lake by isago, tectonic Matano process this dropped since represents lake below 2–3 million is a the years faunas included mean cryp- that as sea provide one remarkable level (Cristescu of examples et the of al., oldest ecological 2010). lakesof diversification In of Lake and terms Matano the speciation formed of world by its and the geomorphology, hardness hosts the of endemic basins the in rocks and the the surrounding softness of uplift tectonic three times a year. 2.2 Lake Matano and Lake Towuti Lake Matano is locatedlatitude. between This 121 lake counts as the seventh deepest lake of the world (Herdendorf, 1982) developed area with lotsinhabited of land residential (Estiaty et areas, al., very 2007). scarce forest patchesportant and for heavily the residents ofand Samarinda its City in short East Kalimantan. distanceincreasing Due and to to steady the poor high land ocean, dischargea cover during this heavy sub-watershed rainfall. often Thisthe small experiences occurrence channel of gradually is slow-paced also flood that inundated most of the residential areas two to The middle part presentsslope, with channel extensive width lowland and ofcountry-style agricultural 100–300 residential areas m, spread areas 10–24 out and m everywherelower vast depth along part distribution with and and of the lakes 0.5–2 Mahakam % depth and Delta and present swampy wide 0–0.5 shrubs. % channel The slope of while 500–850 m with width, regard 10–24 to m land use, the lower sub-basin is a typical with forest and small patches of subsidence agricultural farms dominate the land use. characteristics and the land use, thechannel width upstream of part 40–100 of m Mahakam with River depth presents varies narrow from 5 to 10 m and slope greater than 2 %, to 1 drains an area of 77 095in km Borneo Island andforest ranges the with dramatic Republic elevation of dropsstem, in Indonesia. which the led The first to hundreds riverof the kilometres this rises of formation basin. the in of Then main forms rolling thefifth up hills mountainous hundreds the and kilometres Middle of steep Mahakam its Lake slopes lengthin and and in its Wetlands transforming last the starting into hundred upstream the from kilometres Mahakam the part (MacKinnon Delta et estuary al., 1996). In terms of the channel physical geomorphology, climate and anthropogenic settings. 2.1 Mahakam and Karangmumus Rivers Mahakam watershed is located between 113 uated to assess their reliability and accuracy. 2 Study area This study takes placestream in of Mahakam Mahakam andTowuti which River) Karangmumus are part in Rivers of (one East Maliliareas Lakes tributary oriented Kalimantan, Complex in down- in Indonesia South Figs. Sulawesi, and Indonesia. 1 The Lakes and study 2 Matano represent and typical humid tropics in Asia with di the motivation of this study. InOcean, this Ice-1, study, standard Ice-2 waveform retracking and proceduresserve SeaIce (i.e. water for level Envisat of radarhumid one altimetry small tropics. system) river are In applied and addition,detection to one are careful ob- medium-sized involved to spatial river further and and screen two waveform out lakes low shape in quality selection data. the The and results outlier are then eval- altimetry measurement to monitor important water bodies and therefore, and comprises 5 5 25 15 20 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 350 m ∼ 2832 2831 with 206 m depth, and similar to Lake Matano, also carries 2 Standard optical remote sensing data processing techniques include geometric cor- Satellite radar altimetry measures the geocentric water surface elevation with re- Lake Towuti is recognized as the largest tectonic lake in Indonesia (Russel and Bi- blue colour composite using bands 5, 4 and 3 for Landsat 5 and 7 and bands 6, 5 and 4 water bodies to observe byof satellite the geodetic techniques. river For and instance,sensing lake measurements image, width i.e. are throughgreen-blue carried dark-blue combination out color through of reflected (1) band4 by visual #5-4-3 on the interpretation on Landsat-8, water of Landsat-5 bodies orIndonesian remote Geospatial and in (2) Agency. the Landsat-7, medium-scale red- or (1 : band 50 000) #6-5- topographicrection, maps development and released contrast by of pseudo-natural the colour composite (e.g. red-green- 2011). 3.2 Optical remote sensing and geospatialOptical dataset remote sensing andstudy, especially geospatial in data the determination processing of play physical characteristics an and spatial important boundary role of in this et al., 2006), this studyelevation compares measured the by water level the anomalylevel Ocean, obtained anomaly Ice-1, from water obtained Ice-2 surface from and(i.e. Sea the inverse Ice in-situ barometer, retrackers sea gage with statecorrections measurement. the bias, (i.e. Geophysical ocean water corrections ionospheric tide, correction, polarcorrection) wet tide, and Earth tropospheric instrument tide), correction, propagation to error dry flight corrections tropospheric and (i.e. time Dopplerapplied delay as correction, due it time to is delay ground described as corrections due the and standard antenna procedure center to of obtain gravity) Level-2 products are (ESA, period of observation andprocessing. therefore Water consider level anomaly only represents themean the level water fluctuation during level of the anomaly water period levelwater of for relative observation. surface further to It elevation is its measured obtainedassumption by by removing on altimeter the and the mean of in-situ Ice-1 the gage. as To the prove best the retracking current algorithm for inland waters (Frappart took out the mean water surface elevation measured by satellite altimetry during the spect to the referenceelevation of ellipsoid. the However, field due gage to benchmark relative uncertain to relationship the local between vertical the datum, this research Specifically, this study uses the Envisateters RA2/MWR SGDR for product time that tagging, contains geo-location, param- cant output wave from height, retrackers etc.) (range, at windaltitude. 1 Hz, In speed, addition, plus signifi- the some RA2/MWR 18 Hzthe SGDR waveform parameters also shape such contains selection as the procedure. range 18 TheOctober Hz and dataset waveforms 2010, covers orbital to the corresponding use period to in of cycleRA-2 July 2002 pass, 6 to cycles to and 93 observation (ESA, period 2007). for Table each 1 study describes sites. Envisat a nanosecond. Inradar addition, pulses. it The alsosecond RA-2 measures (i.e. telemetry the 18 Hz) power provides which(ESA, corresponds and 2011). averaged to The shape 18 an averaged of range along-tracknanosecond 18 Hz time sampling the measurements resolution waveforms interval and are reflected per of presents arranged the into default tracking 128 gate gates at with #46 (ESA, 3.125 2007). 3 Materials and methods 3.1 Envisat radar altimetry This study utilizes satelliteSpace radar Agency altimeter (ESA)’s Envisat measurements Radar providedway Altimeter delay by (RA-2). of The The radar RA-2 European determines echo the from two- the Earth’s surface to a very high precision of less than (Vaillant et al., 1997). jaksana, 2012). Located at thecovers downstream an extent end of of 562 the km locally Malili endemic Lakes fauna Complex, due this to lake its nature as one of the ancient lakes. through the Petea River into Lake Mahalona, still in the same Malili Lakes complex 5 5 25 15 20 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (1) thresh- max erent distances (i.e. 500 m er is created to reduce the ff ff and above the WSE min er with di ff erent distance from projected radar footprint ff 2834 2833 ) ) IQR IQR ( ( 1.5 1.5 + − 0.25 Q 0.75 0.25 use shape (Koblinsky, 1993). Additional shapes of Envisat RA-2 returned − Q ff Q = = 0.75 Q min max = Consequently, any measurements below the WSE Considering the fact that inland water surface is smoother than the ocean (Birkett, Once the lake boundaries are identified, a bu WSE WSE elevation as measured by Envisat radar altimetry. IQR Therefore, old were not involved in the further processing. WSE represents the water surface Even after the exclusion of non-qualifiedoutlying waveform from shapes, the some most observations areences value still from range. outliers, In the order mild todefinition outliers obtain of were the the excluded inter-quartile-range dataset from (IQR) each with (Kenney data minimum and array influ- Keeping, following 1947; the Panik, 2012). face, and a mixture2007). In between this water study, and thesidered (quasi) vegetation, as specular, qualified respectively quasi-Brown waveform (Dabo-Niang and toplex flat-patch et perform and shapes al., reliable other are range con- non-classifiedtherefore, measurement discarded shapes while from are the further com- considered process.forms Some as from examples non-qualified this of study waveform these are categorized and presented wave- in Fig. 3. 3.5 Outlier removal, validation and performance evaluation 1998), the (quasi) specularradar shape pulse is returns declaredreflected that as di reflected the by standardradar inland waveform pulse over shapes water inland for water bodies, include2005), quasi-Brown, in flat which patch, contrast generally and complex represent to (Berry a et the al., transition ocean- from land to water, an intermediate sur- unpredictable. The diameter of pulse-limitedabout footprint 1.7 km of (Rees, the 1990;form ESA Envisat 2007). shapes RA-2 Therefore, considering over it that is ainfluenced the necessary smooth by radar to other surface analyse pulse surface is the reflected alongto wave- by with the the di land water surface. surfaceconsider For might that the be the lakes, radius 1 of kmthe the case distance Envisat of to footprint small (half the andlenging, of lake medium-sized and its shore rivers the diameter) should (19–300 waveform is m produced be about width), by enough 850 m. this the In becomes processed very radar chal- pulse reflection might be ries were transformed intoelevation water during level the anomaly period byelevations of of removing observation, the the field due mean gage to benchmark water uncertain relative surface to relationship the between3.4 local the vertical datum. Waveform shape analysis contamination of land surface to the analysed waveforms. 3.3 In-situ water level data Indonesia’s Ministry of Public Workslevel provided of the datasets Mahakam used River for2010) at validation while of Melak water PT siteTowuti (2002–2004) Vale (2002–2012). Indonesia and Similar Karangmumus provides with River validation the (2008– data satellite altimetry for data, Lake the Matano water and level Lake time se- with good contrast between land and water. and 1000 m for lakes) arealtimeter measurements generated can and be included analysed inground based the track on spatial the to processing distance so the between that lakeshores. its the As projected for the river, a 5 m bu for recently launched Landsat 8) were applied to obtain imageries with precise position 5 5 20 15 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (2) (3) cient of corre- ffi is the number of observa- n cient of 0 indicates no corre- ffi ) 2836 2835 ¯ y 1, 1], where coe − 1 indicates total correlation in the same direction − ) i + 1 y − )( ¯ x n ( − i x ( 1 n = i cient is the standard measure of association for continuous type X 2 erent virtual stations in Mahakam River and its middle sub-basin ) i ff ffi = y n xy − i S x are variances for each measurement and ( y 1 S n = i X with v u u t and ). The RMSE is a measure on how well estimation performs over the “truth” value falls within the interval [ y = r x r 1 indicates total correlation in the opposite direction. S xy S is the Envisat water level anomaly x is the in situ measured water level anomaly. − S i S i Once the range measurements that carry non-qualified waveforms excluded, water After all, this finding becomes the second successful satellite radar altimetry ex- To provide a comprehensive understanding on the data processing sequences in this x y The correlation coe Validation and statistical evaluation performance of satellite altimetry water level = surface elevation dataset and subsequently the water level anomalies are calculated remarkable accuracy. Successful retrieval of qualifiedment satellite radar in altimetry this measure- researchcarefully is excludes very all much altimetry supportedthe measurements by water with detailed bodies. projected geographic nadir masking, position which outside of surface elevation at di tributaries retracked using theon Ocean, the Ice-1, GDR are Ice-2 then and selected. Sea The Ice outliers waveform are retrackers defined and excluded from the water ploitation toward very smallet water al. bodies (2012), who (e.g. extracted 80width, 13 m useful also width water without or level validation. measurements less)successful from By exploitation after a of the the river Michailovsky river time with with 40 ofwho 100 m m revealed this the width or water write less, level up, of except Kuo Bajhang no and River Kao other in (2011), Taiwan with studies less indicated than 100 m width with cessed (e.g. waveforms with complexdescribed shape in or Table no 2,waveforms obvious that peak most reflect were of water discarded).the the As level river. trend radar One at pulse particular alltuation returns virtual virtual despite station, produce the stations, i.e. narrow regardless qualified width UM03,measurement the of and even and width the indicates longer useful channel of period the (i.e. of wateris 54 coverage m), level as no as fluc- depicted in-situ indicated in by gage Fig.anomaly. 46 water 5. qualified Unfortunately, level there data available for validation of this extracted water level 4.1 Mahakam River The waveforms resulted from processed returnedand radar only pulses those were matching carefully with selected, the standard waveform shape of water surface were pro- 4 Results and discussion RMSE measurements are carried outments for some are of available the bylation virtual root-mean-square ( stations error where (RMSE) in-situvalue and measure- and the calculated coe following theLi, 2010). standard statistical notation (e.g. Nagler, 2004 and study, Fig. 4 shows each data processing step and their relationship. With tions, lation between two measurements, and of data (deSa, 2007); therefore,altimetry it and is in-situ used water to level measure measurements the as association described between in satellite the following equation. r where: 5 5 25 15 20 10 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | cult to find the crossing ffi 30 m, such as Landsat. In addition, satellite 2838 2837 ∼ erent satellite tracks nearby in fact increases the spatial ff cient of correlation up to 0.97, the satellite radar altimetry presents ffi 1.7 km projected pulse-limited footprint diameter and 35 days revisit pe- ∼ With the coe It is important to note however, that this study did not adjust the magnitude of the To facilitate visual investigation, the correlation between the satellite altimetryWith ob- regard to the retracking algorithm inter-comparison, this study reveals that Ice- With regard to virtual stations at Melak (i.e. Melak01 and Melak02), these virtual Figures 5–7 indicate that river width limits the ability of Envisat RA-2 satellite radar The northeast-southwest orientation ofEnvisat this ground tracks. river However, high makes resolution IKONOS it image (1 di m ground resolution) body and the removalselection of of outliers, the the range measurements only basedstandard intervention on waveform applied its shape waveform to shape for the to(Koblinsky inland strictly dataset et water follow was the body the al., asTherefore, 1993; described there Birkett, must in be 1988; the ample previoussatellite Berry room altimetry studies for et measurement improvement of to al., river increase water 2005; the level, accuracy Dabo-Niang especially of for4.2 et the this study al., area. 2007). Karangmumus River 0.69, is just about thesized average rivers of (200–800 RMSE m obtained width), from as other summarized studies in deal Table with 4. medium satellite altimetry range measurementsof in the any range way. Beside measurements a with careful the spatial projected selection nadir footprint center within the water 1 is not necessarily thesurement, since best SeaIce retracking retracking algorithm algorithm performs forretrackers best inland (i.e. compared water Ocean, to body Ice-1 other standard elevation and mea- Ice-2), according to Table 3. very convenient alternative for monitoring ofeven the medium-sized for river (200–800 poorly-gauged m width), basinstudies, the such magnitude as of the root-mean-square Mahakam error Watershed. (RMSE) Referring reflected in to this other study, i.e. it is backelevation into model show lightly no meandering drastic changes channel. neither In in channel addition, slope,served nor topographic and the map terrain. gage-measured and areretracking algorithm presented digital and in the gage-measured Fig. water 10 level anomaly. as scatter plots between each changes into 13 km straight channel along the heavily populated Melak Town before is heavily meandering just before and along the virtual station Melak01, which then stations are combined sinceis they are no only drastic separated changesteep by gradient). in 14–40 km Having terrain two distance di and andand configuration there temporal of sampling the intensityanomaly channel for from this (e.g. both virtual particular no stations location. reservoir isobserved The plotted or by in combined Fig. the water 8 gage along level installed with station. the right water The level in anomaly MinistryFigure the of 9 middle actually Public also Works’ between indicates gage dynamic these channel station morphology two is in virtual this actually area. stations The channel as shown in Fig. 9. radar altimetry can still measure(Kuo the and water Kao, 2011; level of Michailovskymissing the et cycles, river al., which with 2012). indicates width Table the 2other less variation also due than in shows to 100 temporal various m the coverage number availability fromresolution of of one problem the site in qualified to measurements,. using This an- satellite confirms altimetry the for temporal monitoring inland waters. the water surface (Birkett,size 1998; rivers as Birkett narrow et asthe al., 240 m water 2002), can surface this still boundary study beimageries is monitored reveals identified with and that accurately validated a medium satisfactorily, through given groundaltimeter medium-resolution resolution optical measurement of over aa virtual good temporal station coverage withsence between river the of study width validation periods of datasetneeded (2002–2010). 54 to Still, m for support with (Fig. this previous the 5) particular studies ab- that shows virtual found that station, through alternative careful validation treatment, satellite is are presented Figs. 5–7. altimeter to measure waterolution, level, i.e. especially consideringriod. its While spatial 1 and km seems temporal a res- favorable width to expect typical altimetry radar returns from by removing the mean. The results of water level anomaly observations for each site 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er dis- ff 40 m) through erent bu < ff erent, sometimes irregular waveform ff 2840 2839 ort of satellite altimetry measurement of this study site ff ect the number of qualified waveforms. For instance, from Table 6 one can see the Upon the completion of waveform sorting, the range measurements as performed Similar to the result of satellite altimetry measurements to the small to medium- The waveforms from qualified measurements are further screened out based on the One important note from the e ff noises, especially those inferred by the Ocean retracker. influence the shapes oflake surface the roughness, returned which is altimeterwhich caused waveform. is by mainly One the driven range possible by of cause the crest wind. is and trough the ofby the Ocean, wave, Ice-1, Ice-2observed and water Sea level Ice from retrackers in-situtimetry were gage derived processed station. and Figures and in-situ 14 evaluated gaged and against and water 15 level indicates show anomaly the at the satellite Lake bestis al- Matano and also match Lake obvious Towuti among that the the three Envisat lakes radar studied. altimetry On measurements the present other considerable hand, it a percentage of qualified waveforms for theLake Matano lake and surface Lake with Towuti is distance lowerresult more than calls than those for 1 closer km further to in investigation theand in lakeshore. medium This the lakes complex field in of the tropics, satellite given altimetry the application fact for that small the land cover does not necessarily acceptable waveform shape, while thethe outliers are results also of excluded. TableTowuti. satellite 6 summarizes altimetry waveform qualification over Lakesized Matano river and in the Lake waveforms previous section, that most were of usedalso the to noticed radar that pulse compute separation returns water of produced level distance qualified anomaly to the at lakeshore these seems two does lakes. not significantly It is ular patterns. Considering the dynamicunderstandable, of since the lake water has surface of muchthat the larger lake may extent and and develop river, much wave this more withof is influenced some waveforms by shapes height. wind especially With thoseet the occur al. absence on (2007), of inland further verified waters, study other categorization on than this Dabo-Niang field might worth to consider in the future. typical ocean-like, multi and low peaks, gradually rising and many other kinds of irreg- resulted from satellite altimetrypare measurement to over those the over lakes the are small more to variable medium-sized com- rivers. From Fig. 13, one can see the satellite altimetry technique, especially due to limited numbers of4.3 valid measurements. Lake Matano and Lake Towuti Inland water hasshapes been and known pattern topulse compared signal to produce transmitted the di guished by ocean waveform satellite with shapes based respect fromtances active to Lake sensor. from their Matano Some and response the Lake examples to lakeshore Towuti of radar are at distin- di presented in Fig. 13. Clearly, the waveform shapes very small river cannot bewater evaluated. level Figure anomaly 12 along shows theof with truncated the TRMM time water estimated series level precipitation ofshows time for the lags series the between seems area. the linearly The rainfallit related trend and seems with the not the water viable level rainfall peak. to and These monitor the results plot water conclude also level that of this class of river (width datum, only water level anomaly is presented. is, given the limitation on itssurement spatial still and temporal indicates resolution, the theRiver satellite during inter-annual altimetry 2004 mea- water to 2006, levelthe as in-situ fluctuation measurement compared of record to from the the theMuang, magnitude nearest Gununglingai, Karangmumus available of and gage the precipitation. stations outlet (i.e. In of Pampang, ing addition, the Karangmumus 2008–2010 River) so are available that only dur- the performance of satellite altimetry measurements over this nel. Still, the narrow channel widthful (between satellite 8 radar and altimetry 45 m) measurementand seriously of waveform hampered this success- shape study site. selectionextracted After procedure, from careful Karangmumus there spatial River. filtering are Figuremarizes only 11 the depict 11 the qualified water location, measurements. surface while elevation Table Due 5 to sum- unknown relationship with the vertical allows detailed selection of the altimeter ground tracks that fall within its narrow chan- 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent distance cient) resulted ff ffi at its outlet. Other 1 − cient relative to the in- s 3 ffi erent characteristics. Lake ff erent distance to the lakeshore are illustrated 2842 2841 ff ect of distance from lakeshore to the accuracy of satellite altimetry measurement Compared to other studies, the best RMS error obtained from measurements of Inter-comparison between the available retrackers (i.e. Ocean, Ice-1, Ice-2 and Sea In terms of performance, Envisat radar altimetry measurements over Lake Towuti The result of performance evaluation shows that the initial assumption regarding the Lake Towuti is the largest lake among all lakes in Malili Lakes Complex but possesses To provide an idea on how the satellite altimetry measurements correlate with the in- Physically, the two lakes being studied possess slightly di ff pable to representmedium-sized the rivers, fluctuations of this water study level also of found medium that rivers. small Aside from rivers the (40–200 m width) are 5 Conclusions This study demonstrated thatof satellite medium-sized altimetry (200–800 m isindicated width) capable by rivers to in the monitor thetimetry the high Southeast water and correlation level Asia’s the between humidin the validation tropics, terms dataset water as of level measured thethrough measured performance; on standard by water waveform the retracking level satellite ground. method anomaly al- Even has inferred been by the validated Envisat results and radar vary therefore, altimetry ca- among the small lakessatellite being altimetry studied measurements throughout over the thethe world. small range lakes Table 8 give of the clearly 30 RMS statesas to error 3 that magnitude 50 cm. cm, in Lake as Matano compared is in to fact large the lakes smallest that among produce all lakes RMS listed error in as Table 8. low Ice) cannot suggest anyIce-2 single performed retracker to best inferTowuti. for An water Lake important level conclusion Matano, of thatIce-1 but the could is small Ice-1 be not lakes, drawn retracker necessarily since fromto performed the this medium best best part lakes retracker in for of to Southeast research Lake measure Asia is humid water that tropics. level anomalywater over level small anomaly in this study, i.e. 0.29 m at Lake Towuti, is close to the lowest one in Figs. 18measurements and by 19. the Considering distancesuch the classification from of complicated samples the based results lakeshore, onall from the statistical this distance measures splitting resulted to study from the the does the lakeshore.to performance Table 7 altimeter not the evaluation presents over lakeshore. di recommend from the performance evaluation over di opposite. Two statistical measures (i.e. RMS error and correlation coe best retracker for each lakessee (0.27 Table 7). for This Lake fact is Towuti compared furtherthe to confirmed altimetry by 0.33 the measured for scatterplots and Lake of gage Matano, the measured correlation between water level anomaly ine Figs. 16 and 17. is in-consistent. The satellite altimetryMatano measurement indicates of lower water RMS levelsitu error anomaly gaged and over water Lake higher level anomaly correlation withto coe the the increase lakeshore, of while distance the from satellite the altimetry altimeter footprint measurement over Lake Towuti shows the altimeter measurements as processedwith by the Ocean, gage measured Ice-1, water Ice-2 leveltively. anomaly and for Sea Lake Matano Ice and retrackers Lake Towuti, respec- outperform those on Lake Matano, considering the lower RMS error obtained by the the water level profile fluctuates very gently and ranges inless the depth magnitude of compared 1.2 m. toinfluenced by the wind that Lake comprises Matano.and the Considering lake pushes breeze, its the which blocks precipitating surfacelevel the profile cloud area, cloud of propagation over this this the lake lake also lakeshore is fluctuates (Renggono, gently 2011). in The thesitu ranges field water of gage data, 1.4 m. Figs. 16 and 17 illustrate the correlation between the Envisat radar Matano is a verycipitation gentle and of ultra-deep 2800 mm lake,research into which indicates regulates very that a low nearly maximum mean halfMatano annual discharge of circulates pre- the of through water 133 groundwater within m lake interaction, the outflows which catchment less upstream explains discharge of why compared Lake this to particular its inflow (Hehanussa, 2006). As the result, 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 10.1029/2005GLO22814 erent from one region to ff ort of those regions. ff 2844 2843 , 2002. ), and (2) over lakes, classification of distance from the 2 erence in the number of qualified altimetry measurement. ff This research is primarily supported by the Fulbright PhD Presidential 10.1029/2001JD000609 observable through satellite altimetry, as indicated by reasonably good On the other hand, by learning from obstacles and problems encountered during In contrast with the common assumption as summarized by Frappart et al. (2006), The RMS errors of satellite altimetry measurement of Lake Matano and Lake Towuti dynamics in the107, Amazon LBA26, Basin: doi: application of satellite radar altimetry, J. Geophys. Res., physics (space physics), C. R. Geoscience, 338, 1113–1122, 2006. and Background Review, Slides presented29 at September–1 Workshop October on 2003, Hydrology 2003. from Space, Touluse, from multi-mission altimetry, Geophys. Res.2005. Lett., 32, L16401, doi: rivers and wetlands, Water Resour. Res., 34, 1223–1239, 1998. 1230, 1983. Prog. Nat. Sci., 19, 195–203, 2009. 1494, 2003. suggest significant di involving lakes and reservoirs. the experiment, this study recommendsselection the of following the to range advance measurements future basedstandard studies: on waveform (1) its shape the waveform for shape inland toet strictly water follow al., body the (Koblinsky, 2005; 1993; Dabo-Niang(40–200 Birkett, m 1988; et width) Berry to al., medium rivers 2007)with (200–800 extent m is width), less proposed as than well for 1000satellite as km altimetry small future lake measurements studies (e.g. to those involving the small lakeshore is not recommended since it did not relative to validation measurement, i.e.average 0.33 of m small and lakes 0.27 m,extent being respectively, of studied are Lake about throughout Matano, the theter which world. has bodies It been among is investigated any worth in other noting this studies that study, of is the satellite the altimetry smallest measurement wa- of water level is important to noteanother; however, therefore that a this specific approach situationthe should might development be of be developed permanent for di monitoring each e region, as part of Ice-1 is not necessarily thefor best the retracker Southeast for Asia monitoring humid tropics smallperforms area. water worst It bodies, as is it especially obvious is though, compared thatproduced to the other the Ocean retrackers. retracker best Ice-1, Ice-2 results and in Sea various Ice alternately locations of this study. altimetry-derived water level anomalywater recovered for surface a boundary river isageries with (e.g. identified 54 m Landsat carefully width, with throughvalidated given 30 due the medium-resolution m to ground optical absence resolution). of im- this in-situ Even study gage this provides station, good measurement the indicators was water of level not the anomaly satellite generated in altimetry reability for small rivers. It potentially Birkett, C. M., Mertes, L. A. K., Dunne, T., Costa, M. H., and Jasinski, M. J.:Calmant, Surface S. water and Seyler, F.: Continental surface waters from satellite altimetry, internal geo- Berry, P.A. M., Garlick, J. D., Freeman, J. A., and Mathers, E. L.: Global inland water monitoring Birkett, C. M: Contribution of the TOPEX NASA radar altimeter to the global monitoring of large Brown, O. B. and Cheney, R. E.: Advances in satellite oceanography, Rev. Geophys., 21, 1216– Benveniste, J. and Defrenne, D.: Radar Altimetry Processing for Inland Waters: Introduction Bao, L., Lu, Y., and Wang, Y.: Improved retracking algorithm for oceanic altimeter waveforms, Bamber, J. L: Ice sheet altimeter processing scheme, Int. J. Remote Sens., 15, 925–938, 1994. Alsdorf, D. E. and Lettenmaier, D. P.: Tracking fresh water from space, Science, 301, 1491– References Acknowledgements. Scholarship administered by AmericanInstitute Indonesian for Exchange International Foundation Educationfrom (AMINEF) (IIE). NASA’s and Application In the Science addition,by the this Program Chinese under study Academy the isResearch of Teams partially SERVIR (Grant Sciences/SAFEA project funded No. International KZZD-EW-TZ-05). (NNX12AM85G), byPublic Partnership The Works and grants Program authors of for greatly Republic appreciate Creative level of the data Indonesia used Ministry and in of this PT research. Vale Indonesia, Tbk for providing in-situ water 5 5 20 25 15 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ner, D. G.: Ancient lakes re- ff , 2012. 2846 2845 , 2010. 10.5194/hess-16-2181-2012 10.1111/j.1365-294X.2010.04832.x fall Distribution Pattern of Larona12, Watershed), 17–24, Jurnal 2011 Sains (in dan Teknologi Indonesian). 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J., and Ha Cretaux, J.-F., Jelinski, W., Calmant, S., Kouraev, A. Vuglinski, V., Berge-Nguyen, M., Gen- 5 5 30 20 25 30 15 25 10 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ects in the Seasat altimeter receiver, Int. J. ff 2848 2847 S 397 28 818 m Yes 6-93 2002–2010 SS 46S 297S 3 397 247 m 294 m Yes Yes 8–45 m 8,159 m Yes Yes 6-93 6-93 2002–2010 2002–2010 6-93 6-93 2002–2010 2002–2010 N 89 54 m No 6-93 2002–2010 00 00 00 00 00 00 ths, H. G.: New techniques in satellite altimeter tracking 08 03 21 10 59 ffi 02 0 0 0 0 0 0 17 11 24 30 28 50 ◦ ◦ ◦ ◦ ◦ ◦ , 2012. E 0 E 0 EE 0 0 E 2 E 2 00 00 00 00 00 00 6 0 10 20 58 20 57 0 0 0 0 0 24 ◦ 35 53 47 11 23 ◦ ◦ ◦ ◦ ◦ ner, G. D., and Cristescu, M. E.: The Ancient Lakes of Indonesia: towards ff Envisat RA-2 pass, cycles and observation period for each study sites. Mahakam Watershed Malili Lakes Complex 10.2204/iodp.sd.14.11.2012 systems, III IGARRS 1986and Symposium, Technical Publications Zurich, Branch, Proceedings, 1339–1344, Noordwijk, (ESA ESTEC, SP-254), Scientific 1986. Remote Sens., 8, 1163–1173, 1987. 33, 490–509, 2009. Environmental Studies, SchoolOhio, of 2012. Earth Sciences, The Ohio StateIntegrated Research University, on Columbus, Speciation, Integr. Comp. Biol., 51, 634–643, 2011. cal evolution,doi: and geomicrobiology of a tropical lake, Scientific Drilling, 14, 68–71, Site # Site Name Longitude Latitude Pass River/Lake Width In-Situ Data Cycle Period 1 UM03 114 2a Melak01 115 2b3 Melak02 Karangmumus5 117 115 Towuti 121 4 Matano 121 Table 1. Wingham, D. J., Rapley, C. G., and Gri Wingham, D. J. and Rapley., C. G.: Saturation e Vaillant, J. J., Ha Tseng, K.-H: Satellite Altimetry and Radiometry for Inland Hydrology, Coastal Sea-Level and Tang, Q., Gao, H., Lu, H., and Lettenmaier, D.: Remote sensing: hydrology, Prog. Phys. Geogr., Russel, J. and Bijaksana, S.: The Towuti Drilling Project: paleoenvironments, biologi- 5 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | cient ffi Ice-1Ice-2SeaIce 0.720 0.724 0.685 0.962 0.966 0.970 (#) (%) (#) (%) 2850 2849 Performance evaluation of Envisat RA-2 radar altimetry measurements over Melak Number of qualified and non-qualified altimeter measurements and outliers for study SiteName Covered CyclesMelak Measurement 7–33 Validated Pass Number of Retracker 46 RMSE (m) Coe 2 Ocean Correlation 0.885 0.955 SiteName Cycles Missing Cycles in water body Measurement Measurement Outlier River # width of (m) Measurements Qualified Non-qualified # of UM03Melak01Melak02 9–93 7–93 7–93 34 8 11 51 225 148 220 46 134 97.8 90.2 90.5 5 14 5 2.2 9.5 9.8 N/A 8 0 54 247 m 294 m m virtual stations at Mahakam River (width 247 m). Table 3. Table 2. sites at Mahakam River. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Water Surf 0.4041240.408362 59.63 m 0.407573 55.18 m0.507934 62.64 m0.504634 57.77 m Benanga Reservoir 57.380.405981 m Benanga Reservoir 0.448573 63.33 m0.445263 59.59 m 0.503317 59.57 m 47 m to field0.452076 57.42 gage m 63.810.501533 m 58.76 m − − − − − − − − − − − 2852 2851 erence), RMSE (Root Mean Square Error). ff Qualified Envisat RA-2 altimetry measurements for Karangmumus River. Summary of studies on satellite radar altimetry for water level over river. RMSE (Root Mean Square Error). Cycle Date ID Longitude Latitude Elevation Remarks 8 23 Jun 2002 KM08 117.181540 91323 27 Aug23 2002 13 Jan 200328 KM10 30 Dec 2003 KM1137 117.194581 30 Dec 2003 KM01 117.195384 37 22 Jun 2004 117.157190 KM02 3 May 2005 117.157910 KM09 3 May 2005 117.188367 KM06 117.169721 KM07 117.170441 394249 12 Jul 2005 25 Oct 2005 KM03 27 Jun 2006 KM05 117.158610 KM04 117.171486 117.159139 ReferenceKoblinsky et al. (1993)Birkett et al. (1998, 2002)Kouraev et al. (2004) Amazon AmazonFrappart Basin Basin et al. (2006)Kuo and Kao N/A 1.5 (2011) kmMichailovsky Location et Ob’ al. River (2012)Sulistioadi (2013) Mekong River Zambezi River Bajhang T/P River 450 m 80 Geosat m River 3 Width km 100 m Satellite/Sensor Mahakam River Reported Error Envisat, 279 (m) m T/P Envisat STDE: T/P Jason-2 0.31–1.68 m RMSE: 0.60 m RMSE: 0.23 m, RMSE: Envisat 0.15 m RMSE: 0.72 m STDE: 0.31 m %: 8 % RMSE: 0.69 m STDE (Standard Deviation of Error), % (% di Table 5. Table 4. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | cient (m) Outliers #%#% ffi Ice-1Ice-2SeaIce 0.221 0.276 0.341Ice-1Ice-2 0.858SeaIce 0.836 0.538 0.760 16.35 % 0.723 0.745Ice-1Ice-2 0.624SeaIce 0.458 0.647 0.417 12.56 % 0.667 0.666Ice-1Ice-2 0.535SeaIce 0.517 0.858 0.518 14.29 % 0.876 0.750Ice-1 0.346Ice-2 0.322 0.526 14.62 % SeaIce 0.886 0.867 0.880Ice-1Ice-2 0.348SeaIce 0.369 0.884 0.342 10.05 % 0.864 0.859Ice-1Ice-2 0.337SeaIce 0.375 0.780 0.380 8.38 % 0.761 0.761Ice-1Ice-2 0.521SeaIce 0.514 0.924 0.529 6.27 % 0.910 0.908 0.269 0.289 0.294 7.40 % 2854 2853 1 km1 km 989 805 81.4 2450 1353 184 54.3 1137 18.6 45.7 115 156 500 m500 m 453 416 91.8 1314 786 37 59.8 528 8.2 40.2 68 79 > > < < Distance Measurement No of 500 m–1 km500 m–1 km 253 215 85.0 1328 764 38 57.5 15.0 564 42.5 27 64 Lake Validated Correlation RMSE No/% of 1000 m 73 Ocean1000 m 0.692 0.493 115/805 73 Ocean 0.689 0.611 156/2490 SiteLake Matano 81590–500 m width (m) 8–79 Cycles measurement500–1000 m Retracker coe > 75Merged 71 OceanLake Towuti0–500 28 m 818 0.202 Ocean 8–79 0.605 0.995500–1000 m 68/416 75 0.554 27/215 > Ocean 75Merged 0.884 71 0.317 Ocean 210/1436 0.851 Ocean 0.920 0.416 79/786 75 0.275 64/764 Ocean 0.920 0.274 299/4040 Performance evaluation of Envisat RA-2 radar altimetry measurements over Lake The number of qualified and non-qualified altimeter measurements and outliers over Lake Matano 8159Lake 8–79 Towuti 28 818 8–79 Location Width Cycle to Shore Within water body Qualified Non-Qualified Outlier Table 7. Matano and Lake Towuti. Table 6. Lake Matano and Lake Towuti. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | T/P, ERS-1TOPEX/Poseidon RMSE: 0.10 m TOPEX/Poseidon RMSE: 0.03 m RMSE:TOPEX/Poseidon 0.21 m RMSE:Envisat 0.08 m EnvisatEnvisatTOPEX/Poseidon RMSE:T/P, 0.13 Jason-1 m RMSE: 0.09 m Envisat RMSE: 0.30 m Envisat Mean Error: 0.31 RMSE: m 0.15 m Envisat RMSE: 0.06 m RMSE: 0.32 m RMSE: 0.29 m TOPEX/Poseidon RMSE: 0.50 m 3 2 2 10 3 2 km × 10 2 2 2 2 2 6 2 2 2 × 10 × 2856 2855 Rukwa and Kyoga 75–80 Lake Towuti 562 km Michigan, HuronErieLake St Clair Large Geosat RMSE: 0.11 m Geosat Geosat RMSE: 0.17 m RMSE: 0.13 m Summary of studies on satellite radar altimetry for water level over lakes. Study Sites at Mahakam Watershed, East Kalimantan, Indonesia. RMSE (Root Mean Square Error). Mercier et al. (2002) Victoria,Zhang Tanganyika Malawi et and al. Turkana (2006)Medina et 131–390 al. (2008)Munyaneza et al. (2009)Cai Dongting and Lake Ji Lake (2009) Kivu LakeGuo Izabal et al. (2009)Troitskaya et al. (2012)Tseng et al. (2013) Poyang Gorki LakeSulistioadi Reservoir (2013) Hulun Lake Qinghai Lake Lake Matano 2623 km 717 km 2400 km 1358 km 20 290 km 2339 km 4186 km 164 km ReferenceMorris and Gill (1994a) Superior, OntarioMorris and Gill Location (1994b)Korotaev et al. (2001) Great Lakes Black SeaCoe and Birkett (2004) Lake Chad Large Geosat Lake Extent Satellite/Sensor 436 402 km RMSE: Reported 0.09 m Error 2.5 Topex/Poseidon RMSE: 0.03 m ∗ Table 8. Fig. 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2858 2857 General categories of waveform shapes. Study Sites at Malili Lakes Complex, South Sulawesi, Indonesia. Fig. 3. Fig. 2. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2860 2859 Data processing workflow. ENVISAT Observed Water Level Anomaly at Site UM03 (river width 54 m) as measured Fig. 5. by Envisat RA-2 and processed by Ice-1 retracker. Fig. 4. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2862 2861 ENVISAT Observed Water Level Anomaly at Site Melak02 (river width 294 m) as mea- ENVISAT Observed Water Level Anomaly at Site Melak01 (river width 247 m) as mea- Fig. 7. sured by Envisat RA-2 and processed by Ice-1 retracker. sured by Envisat RA-2 and processed by Ice-1 retracker. Fig. 6. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2864 2863 Location of Envisat virtual stations and in-situ water level gage stations at Melak Town. Water level anomaly at Melak as observed by two Envisat passes and retracked by four Fig. 9. Fig. 8. retrackers; compared with in-situ water level anomaly. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2866 2865 Overview of Karangmumus Sub-watershed and Envisat ground track with background Correlation between water level anomaly measured by Envisat altimeter and processed Fig. 11. of Landsat-7 image ofof January white 2007 box (left) of the and left IKONOS image). of February 2002 (right, in the extent Fig. 10. with Ocean (top left), Ice-1and in-situ (top water right), level Ice-2 measurement (bottom over left) Melak. and Sea Ice (bottom right) retrackers Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2868 2867 er distances to the lakeshore. ff Distinguished waveform shapes as reflected by Lake Matano and Lake Towuti at dif- Water level anomaly of Karangmumus River from Envisat RA-2. Fig. 13. ferent bu Fig. 12. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2870 2869 Water level anomaly at Lake Towuti as measured by Envisat RA-2 and processed by Water level anomaly at Lake Matano as measured by Envisat RA-2 and processed by Fig. 15. all retracker, compared with in-situ measurement. Fig. 14. all retracker, compared with in-situ measurement. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2872 2871 Correlation between water level anomaly at Lake Matano as measured by Envisat RA- Correlation between water level anomaly at Lake Towuti as measured by Envisat RA-2 Fig. 17. altimeter and processed with Ocean(bottom right) (top retrackers. left), Ice-1 (top right), Ice-2 (bottom left) and Sea Ice Fig. 16. 2 altimeter and processedIce with (bottom Ocean right) retrackers. (top left), Ice-1 (top right), Ice-2 (bottom left) and Sea Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

40 40

2 radar altimetry measurements over Lake 2 radar altimetry measurements over Lake 2 radar altimetry measurements over Lake 2 radar altimetry measurements over Lake - - - - RA RA RA RA

2874 2873 Envisat Envisat Envisat Envisat Towuti, classified by the by the to lakeshore the Towuti, classified distance The performance of of performance The Matano, classified by the to lakeshore the classified distance Matano, The performance of of performance The Matano, classified by the to lakeshore the classified distance Matano, by the to lakeshore the Towuti, classified distance The performance of of performance The of performance The

The performance of Envisat RA-2 radar altimetry measurements over Lake Towuti, The performance of Envisat RA-2 radar altimetry measurements over Lake Matano, Figure 19 Figure 18

Figure 18 Figure 19 6 3 4 5 7 8 2 1 2 6 7 8 1 3 4 5 Fig. 19. classified by the distance to the lakeshore. Fig. 18. classified by the distance to the lakeshore.