I was not actually expecting an answer from Praveen but it cames (and I realized later that this record is easy to obtain having a WEB of SCIENCE and SCOPUS account) Results were stored in a file that you can retrieve here.

Being the most cited does not necessarily means being the best papers. Some very good papers could have been published very recently, and still not having enough citations to rank among the first ones. Some very good papers could be too specialistic to be read by most of us fluency. Besides some topic are of more broad interest than others, and this increase their citations' rates. However, after all of these disclaimers, here there are the papers, some statistics, and comments. The paper grouped, for broad sub-fields, are about:

calibration and uncertainty 8

evapotranspiration and ecohydrology 6

experimental hydrology 2

geochemistry 5

geomorphology 22

groundwater 78

infiltration and vadose zone 29

other 10

precipitation 5

mathematical ans statistical 13

surface water 23

The dominance of groundwater papers is apparent, but this is probably a inheritance of the lated eighties and nineties. While browsing the recent papers there is more equilibrium between the fields covered.

Grouped for year of publication, the are distributed as shown below.

The figures shows that they cover all the decades of publication of WRR from 1965 to 2003.

Grouped per decades these 201 paper are

1960 16

1970 36

1980 75

1990 68

2000 6

So, the 20 higher cited papers are (the other can be seen in the xls file):

- MUALEM, Y, NEW MODEL FOR PREDICTING HYDRAULIC CONDUCTIVITY OF UNSATURATED POROUS-MEDIA, 1976, cit: 1818

- TOPP, GC, DAVIS, JL, ANNAN, AP, ELECTROMAGNETIC DETERMINATION OF SOIL-WATER CONTENT - MEASUREMENTS IN COAXIAL TRANSMISSION-LINES, 1980, cit: 1800

- BEVEN, K, GERMANN, P, MACROPORES AND WATER-FLOW IN SOILS, 1982, cit:1058

- CLAPP, RB, HORNBERGER, GM, EMPIRICAL EQUATIONS FOR SOME SOIL HYDRAULIC-PROPERTIES,1978, cit: 1034

- GELHAR, LW, AXNESS, CL, 3-DIMENSIONAL STOCHASTIC-ANALYSIS OF MACRODISPERSION IN AQUIFERS, 1983, cit: 986

- RITCHIE, JT, MODEL FOR PREDICTING EVAPORATION FROM A ROW CROP WITH INCOMPLETE COVER, 1972,cit: 931

- DUAN, QY, SOROOSHIAN, S, GUPTA, HV EFFECTIVE AND EFFICIENT GLOBAL OPTIMIZATION FOR CONCEPTUAL RAINFALL-RUNOFF MODELS, 1992, cit: 776

- SUDICKY, EA, A NATURAL GRADIENT EXPERIMENT ON SOLUTE TRANSPORT IN A SAND AQUIFER - SPATIAL VARIABILITY OF HYDRAULIC CONDUCTIVITY AND ITS ROLE IN THE DISPERSION PROCESS,1986, cit:645

- HIRSCH, RM, SLACK, JR, SMITH, RA, TECHNIQUES OF TREND ANALYSIS FOR MONTHLY WATER-QUALITY DATA, 1982, cit:577

- Legates, GJ, McCabe, DR, Evaluating the use of goodness-of-fit measures in hydrologic and hydroclimatic model validation, 1999, cit:573

- CELIA, MA, BOULOUTAS, ET, ZARBA, RL, A GENERAL MASS-CONSERVATIVE NUMERICAL-SOLUTION FOR THE UNSATURATED FLOW EQUATION, 1990, cit:564

- GELHAR, LW, WELTY, C, REHFELDT, KR, A CRITICAL-REVIEW OF DATA ON FIELD-SCALE DISPERSION IN AQUIFERS, 1992, cit:554

- YEH, WWG, REVIEW OF PARAMETER-IDENTIFICATION PROCEDURES IN GROUNDWATER HYDROLOGY - THE INVERSE PROBLEM, 1986, cit: 546

- COSBY, BJ, HORNBERGER, GM, GALLOWAY, JN, WRIGHT, RF, MODELING THE EFFECTS OF ACID DEPOSITION - ASSESSMENT OF A LUMPED PARAMETER MODEL OF SOIL-WATER AND STREAMWATER CHEMISTRY, 1985, cit: 530

- FREEZE, RA, STOCHASTIC-CONCEPTUAL ANALYSIS OF ONE-DIMENSIONAL GROUNDWATER FLOW IN NONUNIFORM HOMOGENEOUS MEDIA, 1975, cit: 528

- JACKSON, RD, IDSO, SB, REGINATO, RJ, PINTER, PJ, CANOPY TEMPERATURE AS A CROP WATER-STRESS INDICATOR, 1981, cit:506

- Tarboton, A new method for the determination of flow directions and upslope areas in grid digital elevation models, DG, 1997, cit: 477

- CARSEL, RF, PARRISH, RS, DEVELOPING JOINT PROBABILITY-DISTRIBUTIONS OF SOIL-WATER RETENTION CHARACTERISTICS, 1988, cit: 467

- COSBY, BJ, HORNBERGER, GM, CLAPP, RB, GINN, TR, A STATISTICAL EXPLORATION OF THE RELATIONSHIPS OF SOIL-MOISTURE CHARACTERISTICS TO THE PHYSICAL-PROPERTIES OF SOILS, 1984, cit: 451

RICHARDSON, CW, STOCHASTIC SIMULATION OF DAILY PRECIPITATION, TEMPERATURE, AND SOLAR-RADIATION, 1981, cit: 440

Reading the list of these paper is apparent that the first ones belong to a interdisciplinary area of interest that cover hydrology, soil science, and, at least, agricolture. The inverse modelling is also a pretty relevant topic, while surface hydrology is not present (except for Tarboton's paper, which however is on DEM treatment): which is a surprise to me!

The mean number of citations is around 300. So, a high cited paper, at least for WRR should have around 200 citations (unfortunately, my papers are still away from this). A summary of the statistics is:

Min. 1st Qu. Median Mean 3rd Qu. Max.

184.0 208.0 241.0 302.9 318.0 1818.0

The ten most recent papers among the most cited are:

- Houser, PR, Shuttleworth, WJ, Famiglietti, JS, Gupta, HV, Syed, KH, Goodrich, DC, Integration of soil moisture remote sensing and hydrologic modeling using data assimilation, 1998, cit: 185

- Legates, DR, McCabe, GJ, Evaluating the use of goodness-of-fit measures in hydrologic and hydroclimatic model validation, 1999, cit: 573

- Nepf, HM, Drag, turbulence, and diffusion in flow through emergent vegetation, 1999, cit: 239

- Western, AW, Grayson, RB, Bloschl, G, Willgoose, GR, McMahon, Observed spatial organization of soil moisture and its relation to terrain indices TA 1999, cit: 209

- Rodriguez-Iturbe, I, Ecohydrology: A hydrologic perspective of climate-soil-vegetation dynamics, 2000, cit: 213

- Iverson, RM, Landslide triggering by rain infiltration, 2000, cit:207

-McArthur, JM, Ravenscroft, P, Safiulla, S, Thirlwall, MF, Arsenic in groundwater: Testing pollution mechanisms for sedimentary aquifers in Bangladesh 2001, cit: 279

-Zhang, L, Dawes, WR, Walker, GR, Response of mean annual evapotranspiration to vegetation changes at catchment scale, 2001, cit: 274

-Zhang, XB, Harvey, KD, Hogg, WD, Yuzyk, TR, Trends in Canadian streamflow, 2001, cit: 201

- Vrugt, JA, Gupta, HV, Bouten, W, Sorooshian, S 2003, A Shuffled Complex Evolution Metropolis algorithm for optimization and uncertainty assessment of hydrologic model parameters

Neither between these appears a paper on surface waters. However, it is interesting to note that the topics covered are different from those of the highest cited papers. Meaning probably that each decade has its focus.

Yearly citations rate show that the first group of papers are really outliers with respect to the others. However the mean number of citations per year is around 12, and if your papers has more that 5 citations per years, there is some hope that sometimes in the future it could enter in this rank.

Min. 1st Qu. Median Mean 3rd Qu. Max.

4.244 7.960 10.420 12.300 14.190 56.250

The ten papers with the highest annual average citations' rate are:

- TOPP, GC, DAVIS, JL, ANNAN, AP, ELECTROMAGNETIC DETERMINATION OF SOIL-WATER CONTENT - MEASUREMENTS IN COAXIAL TRANSMISSION-LINES, 1980, cit: 1800, citation rate: 56.25,

- MUALEM, Y, NEW MODEL FOR PREDICTING HYDRAULIC CONDUCTIVITY OF UNSATURATED POROUS-MEDIA, 1976, citation rate: 50.5

- DR, McCabe, GJ, Evaluating the use of goodness-of-fit measures in hydrologic and hydroclimatic model validation Legates, 1999,cit: 1800,cit: , citation rate: 44.01

- DUAN, QY, SOROOSHIAN, S, GUPTA, V, EFFECTIVE AND EFFICIENT GLOBAL OPTIMIZATION FOR CONCEPTUAL RAINFALL-RUNOFF MODELS, 1992, cit: 776, citation rate:38.8

- BEVEN, K, GERMANN, P, MACROPORES AND WATER-FLOW IN SOILS, 1982, cit: 1058, citation rate: 35.3

- GELHAR, LW, AXNESS, CL , 3-DIMENSIONAL STOCHASTIC-ANALYSIS OF MACRODISPERSION IN AQUIFERS, 1983, cit: 986, citation rate: 34

- Tarboton, DG, A new method for the determination of flow directions and upslope areas in grid digital elevation models, 1997, cit: 477, citation rate: 30.4

- CLAPP, RB, HORNBERGER, GM, EMPIRICAL EQUATIONS FOR SOME SOIL HYDRAULIC-PROPERTIES, 1978 cit: 1034, citation rate: 24

- Gupta, HV, Sorooshian, S, Yapo, PO , Toward improved calibration of hydrologic models: Multiple and noncommensurable measures of information, 1998, cit. 402, citation rate: 23.3

- GELHAR, LW, WELTY, C, REHFELDT, KR, A CRITICAL-REVIEW OF DATA ON FIELD-SCALE DISPERSION IN AQUIFERS, 1992, cit: 554, citations rate: 19.2

Finally, the authors who wrote these papers are 337. Most of them appear once. Those who compare more than two times are:

12 ABRIOLA, LM 3

12 BEVEN, K 3

12 CELIA, MA 3

12 COSBY, BJ 3

12 DAGAN, G 3

12 DIETRICH, WE 3

12 GORELICK, SM 3

12 GRAYSON, RB 3

12 IDSO, SB 3

12 KITANIDIS, PK 3

12 MCMAHON, TA 3

12 NIELSEN, DR 3

12 PAPADOPU.IS 3

12 SUDICKY, EA 3

12 VANGENUCHTEN, MT 3

12 WITHERSPOON, PA 3

12 WRIGHT, RF 3

7 FREEZE, RA 4

7 MANDELBROT, BB 4

7 RODRIGUEZ-ITURBE, I 4

7 SOROOSHIAN, S 4

3 GUPTA, HV 5

3 GUTJAHR, AL 5

3 HORNBERGER, GM 5

3 NEUMAN, SP 5

3 MONTGOMERY, DR 6

2 WALLIS, JR 6

1 GELHAR, LW 12

I must say that I know most of the Authors, many of them personally, since their work inspired mine, and just by googling their names it is clear that some of them gave some exceptional contribution even in other journals. So despite the many disclaimer citations say something. Someone of my hydrological heroes is missing: but doing benchmark papers is probably is slightly a different thing than writing a highly cited paper.